Anycubic Kobra S1: Known Issues and How to Fix Them

The Anycubic Kobra S1 is an enclosed CoreXY printer with a 250×250×250 mm build volume, speeds up to 600 mm/s, a 320 °C hotend, a 120 °C bed and the ACE Pro 4-color system. It's reliable and prints great out of the box, but it has its own quirks that other printers don't: ACE Pro jams, PETG clogs and its own on-screen error codes. This guide covers only the issues that are unique to the S1 and how to fix them. Generic FDM problems (stringing, warping, first layer) are linked as dedicated guides at the end.

Almost every S1 fault shows on the screen as a code like CODE: 11518 with a short description. Below are the nine most common problems — from easy to hard — plus an error-code table at the end. Most facts come from the official Anycubic error-code database, the ACE Pro clog guide and the hotend cleaning guide, plus reviews from Tom’s Hardware, VoxelMatters and 3DWithUs.

1. Filament jams in the ACE Pro (codes 11518, 11511, 11519)

The most common complaint from Combo owners is filament jamming inside the ACE Pro feed system. The print pauses with 11518 "Filament clogging detected" or 11511 "Feeding timeout". Sometimes you hear a loud clunk when the mechanism can't grab the filament, and 11519 "Filament tangle detected" means the coils crossed on the spool. It usually happens with incorrect loading, wet or brittle filament, and tangled spools.

1. Restart the ACE Pro. The feed gear resets to zero and opens a gap so you can pull the filament out by hand. This is Anycubic's official first step and it fixes most cases.
2. If filament is stuck in the gear, loosen the two cover screws with an S2.5 Allen key, then turn the gear by hand while pulling the filament.
3. If it's stuck in the buffer, remove the blue clasp and PTFE tube, loosen the buffer cover screws with S2.5 and remove the buffer with S2.0, then pull the filament out.
4. Check the spool: rewind it, undo any crossed coils and make sure the filament unwinds freely.
5. Wet PETG or nylon gets brittle and snaps during feeding — dry the filament before printing (see the drying guide at the end).

You'll need S2.0 and S2.5 Allen keys to open the ACE Pro. For loading and running the multicolor system, see our ACE Pro guide.

2. Hotend clogs, especially on PETG (codes 11518, 11512)

The extruder clicks and turns but little to no plastic comes out — a classic clog. On the S1 it loves to happen on PETG: during retraction, brittle or old filament snaps right inside the print head and the broken piece jams the channel. In the The Gadgeteer review, an old-PETG clog took about two hours to fix. Key point: early firmware itself caused frequent PETG clogs — Anycubic fixed it in V2.6.8.8, so update Kobra OS first.

1. Update the firmware — V2.6.8.8 fixed frequent PETG clogs and V2.6.9.2 optimized purge length.
2. Raise the hotend temp slightly above normal (e.g. 250 °C for PLA) and hit Extrude — the clog often just pushes out.
3. If that fails, remove the print head cover, unplug the part-cooling fan cable, remove the blue clip and PTFE tube, and cut the filament.
4. Heat the nozzle to 250 °C, clear it with a steel needle, then push the clog out with a piece of filament (cold pull). For a stubborn clog, run a long S1.5 Allen key down the throat.
5. For PETG, lower retraction speed and distance in the slicer and keep the filament dry — wet PETG is brittle and snaps in the head.
6. If the nozzle is damaged (scored, worn tip), swap it for a fresh quick-release nozzle. For abrasives, go straight to hardened steel.

Printing carbon fiber, glow-in-the-dark or other abrasive filament? A stock brass nozzle wears out in tens of hours, the bore grows and quality drifts. Fit a hardened steel nozzle — it's quick-release and swaps out with the lever in a minute. We cover the general mechanics of clogs in the nozzle clogging guide.

3. Huge purge waste and slow multicolor printing

Multicolor printing through the ACE Pro looks great but costs plastic and time. In the VoxelMatters test, a 10.9 g Benchy generated 183 g of purge waste — a 17x overspend. Each color change takes about two minutes, so a one-hour model easily balloons to 9+ hours. Worse, the stock Anycubic Slicer Next doesn't show the real purge volume, so you plan material use blind.

1. Update the firmware — recent versions optimize purge length on color changes.
2. Use fewer colors: two or three instead of four cuts the number of swaps and the waste dramatically.
3. In the slicer, flush the purge into infill or a wipe tower instead of into the air — some plastic goes into the part.
4. Group colors by layer so the printer switches spools less often.
5. Only print multicolor where it truly matters — everything else is faster and cheaper in a single color.

For tuning color changes and purge with minimal waste, see the ACE Pro multicolor guide.

4. Camera and remote monitoring drop out with timeouts

The built-in camera and app monitoring are flaky. In the 3DToday review the webcam dropped out on timeout about 60% of the time, and The Gadgeteer complained of constant timeout errors in the mobile app. Sometimes when you enable AI monitoring or timelapse the printer doesn't see the camera at all. The cause is almost always a weak or congested Wi-Fi connection.

1. Connect the printer to 2.4 GHz Wi-Fi with a strong signal — 5 GHz penetrates walls worse and drops more often.
2. Turn off LAN mode before binding the printer in the app — in LAN mode binding and updates may fail.
3. Restart the printer and reconnect the camera afterward — that restores the stream after a connection error.
4. Keep the phone and printer on the same network and update the firmware — some connection issues are fixed by updates.
5. If the camera isn't detected at all ("Camera is not connected"), check the network and connection status, and contact support if it repeats.

5. False AI detection alarms (codes 11801, 11802)

The AI camera catches spaghetti and foreign objects, but it sometimes cries wolf. Code 11801 "Spaghetti error detected" flags a print failure (sometimes falsely), and 11802 "Foreign object detected" claims there's something on the bed. In the 3DWithUs test there were two false positives over a 29-hour print, both cleared with Resume. False alarms are more common on dark, translucent or glossy filament.

1. If the print is fine, tap Resume/Continue and the job carries on.
2. Lower the AI detection sensitivity in the camera settings on the printer screen.
3. Keep the bed clean before starting — scraps and debris get flagged as a foreign object.
4. Update the firmware: Anycubic reduced false detections through Kobra OS updates.

6. Color bleed and marks on multicolor prints

On the first layer of a multicolor model colors sometimes bleed into each other, and traces of the previous color linger on the surface. That's a sign of insufficient purging on color changes. Good news: Anycubic specifically fixed first-layer color mixing and surface residue in firmware V2.6.8.8, so the baseline is fixed by updating.

1. Update the firmware — V2.6.8.8 fixed first-layer color mixing and material residue on multicolor surfaces.
2. Increase the purge volume for high-contrast transitions (e.g. dark to white).
3. Clean the silicone wiper and eject chute — dried purge smears the surface.
4. Where possible, print the first layer in a single color so transitions don't spoil the base.

7. LeviQ 3.0 auto-leveling failures (codes 10237, 11534)

LeviQ 3.0 with the in-nozzle strain gauge is usually accurate, which is why the S1's first layer rarely misbehaves. But if there's a blob on the nozzle tip or oily fingerprints on the bed, calibration goes wrong: the screen shows 10237 "Auto leveling error, verify sensor" or 11534 "Auto leveling failed". VoxelMatters explicitly noted that first-layer issues only show up from oily fingerprints on the bed or a bed that's too cold.

1. Clean any burnt blob off the nozzle tip at printing temperature — a blob at the moment of contact throws off the measurement.
2. Wipe the bed with isopropyl alcohol and don't touch it with bare hands — finger grease hurts both adhesion and calibration.
3. Make sure the nozzle isn't oozing before calibration, and preheat the bed to working temperature.
4. Redo auto-leveling. If the error keeps coming back, check and if needed replace the print head strain gauge.

If the first layer still drifts after calibration, we break down adhesion and Z-offset in the first layer guide.

8. Early-batch QC: dents, wiring, print-head cover (11407, 11412)

Some early units have shaky factory quality. Tom’s Hardware noted dents on the body and frayed wires out of the box. Contact issues show up as 11407 "Device startup failed" (check print head and driver board connectors), 11412 "MCU disconnected", 11817 "E-axis short circuit" and 10411 "TMC/extruder overheat". And the fact that firmware V2.7.1.4 added "detection for a detached print head housing" is a clear hint that the head cover came loose on some early machines.

1. Inspect the printer carefully when unboxing — dents, impact marks or frayed insulation are grounds to contact support right away.
2. For startup errors (11407, 11412), power down and reseat the print head and driver board cables in the correct orientation per Anycubic's instructions.
3. For overheat errors (10411), verify the heatsink and board cooling fans are spinning and let the electronics cool down.
4. Make sure the print head cover is seated and clicked in; update the firmware so detached-cover detection works.
5. Don't fix factory defects yourself — that's a warranty case. Contact your official reseller or Anycubic support.

9. Spool squeak and ACE Pro feed noise (11509, 11521)

After roughly a hundred hours the spools in the ACE Pro start to squeak, and sometimes you hear loud noises when the mechanism can't grab the filament properly. Code 11509 "ACE responses timeout" points to ACE Pro power or signal wiring, while 11521 "Color engine motor abnormal" points to a stuck feed motor. It's usually fixable without spare parts.

1. Check the spool seating — a skewed spool adds resistance and squeak.
2. Lubricate the spool axle with a thin layer of grease to kill the squeak.
3. Straighten the PTFE tubes between the ACE Pro and the head — sharp bends raise feed force.
4. Check ACE Pro power and signal cabling for code 11509; for 11521, restart the color engine unit.

Anycubic Kobra S1 error codes: table

The S1 shows faults as a numeric code on the screen. Below are the most common codes, what they mean and what to do. The full list of 52 codes is in the official Anycubic database.

Common 3D printing problems — detailed guides

Beyond the S1's own quirks, you'll also run into the usual FDM problems. We cover each in a dedicated in-depth guide that applies to any printer:

• Nozzle clogs: causes and prevention
• First layer and bed adhesion
• Stringing and wisps
• Warping and lifting corners
• Under- and over-extrusion
• Layer shifting and ghosting
• How to dry filament properly
• 3D printer maintenance

We also recommend: the Anycubic Kobra S1 review, the Kobra S1 vs Bambu Lab P1S comparison, the ACE Pro multicolor guide, the OrcaSlicer setup and the ventilation guide for ABS/ASA.

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