[BUG] Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet - Hardware, firmware and software help

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

hyiger — Mon, 04 May 2026 16:21:15 +0000

Posted by: @ruebarb
Prusa's response after months and numerous cases made on github, was to remove the G28 "Q" from the C1l config start G code, and back to the standard G28 until they firgure out what is wrong with the firmware. Prusa did not make any announcement of this issue, did not include it in any comments when releasing the updated config, as to why and what critical change was made. Just rolled out the updated config, letting any existing users out there with profiles based on the old config, continue to have these problems. Everything's Fine

That's the biggest issue I run into. My start g-code is heavily modified and every so often I have to diff it with the stock profile to see what has changed.

RE:

Ruebarb — Mon, 04 May 2026 14:04:04 +0000

Prusa's response after months and numerous cases made on github, was to remove the G28 "Q" from the C1l config start G code, and back to the standard G28 until they firgure out what is wrong with the firmware. Prusa did not make any announcement of this issue, did not include it in any comments when releasing the updated config, as to why and what critical change was made. Just rolled out the updated config, letting any existing users out there with profiles based on the old config, continue to have these problems. Everything's Fine

RE:

chris jordan — Mon, 04 May 2026 06:07:31 +0000

This isn’t something you should brush off as a rare glitch—you’re dealing with a potentially hardware-damaging firmware issue: based on your description, the “Retry” path in the nozzle clearing routine is skipping or misapplying the Z re-homing/offset step, which means the printer is continuing with an incorrect Z reference and physically driving the nozzle into the sheet; the fact that it only happens after a failed first cleaning strongly suggests a state-handling bug (likely the machine assumes it’s already in a safe Z when it isn’t). Until this is fixed, the practical move is to never use Retry—abort the print, manually re-home (full XYZ), and restart, because continuing risks cumulative damage to your sheet and potentially the nozzle; also, your inability to reproduce it on demand doesn’t weaken your case—it actually reinforces that this is a conditional firmware edge case, so you should push support with logs (if available) and exact sequence details rather than trying to “force” it again, because deliberately triggering failures just to capture video is how you end up damaging your machine further.

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

Same Old Shane — Thu, 12 Mar 2026 03:48:53 +0000

just a FYI, I submitted this post to the product team for review.

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

Ruebarb — Wed, 11 Mar 2026 22:22:53 +0000

The redit post linked above finally got some attention from Prusa, they also got a dev looking at the github post

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

Kubarlov — Wed, 11 Mar 2026 18:06:29 +0000

Don't worry, software specialists are informed 😊

I have had C1L for a month and initially I had the same problem (the same drawing of the nozzle on the table when cleaning), but I also saw that the problem is known and the team is trying to solve it. After the last update (about a week ago), the nozzle cleaning error disappeared for me - until today, when it appeared again. The circumstances in which the error reappeared in my case were such that I initiated the printout via Connect as "print again", while all previous printouts (since the software update) were initiated via Connect.

I contacted the technical service department via chat about this matter, shared my observations and received a reply that in fact the problem still occurs when "print again". After this nice and constructive exchange of information, I initiated another print via Connect by sending a new file for printing - the print started with proper nozzle cleaning.

Try my method, maybe it will work too. Also try my method of observing and writing down your own activities for constructive communication with technical support - these also include activities that are trivial from our point of view, but are important for the printer software. In my case, the "print again" function turned out to be important, i.e. related to the occurrence of a problem. If the problem on your side is solved when you don't use this function, we don't even have to bother the technical support and we can calmly wait until the next update 😊

If there are any other observations regarding this problem, I think it is worth collecting them here in this thread for the technical department to see. Here is a video of the nozzle drawing on the bed in my printer during a nozzle cleaning error (this morning):

https://drive.google.com/file/d/1SZI_cm5a_G67kkqXobKFbSMLPeAmybvt/view?usp=sharing

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

alphasigma — Wed, 11 Mar 2026 06:35:24 +0000

@Ruebarb: Yes, you already postetd the link to Github where the issue was described and a soulution presented in January (!). I didn't read this Github post, have to admit never done it...just stumbled over the Reddit post...

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

alphasigma — Wed, 11 Mar 2026 06:23:36 +0000

Very, very interesting:

https://www.reddit.com/r/prusa3d/comments/1rqib31/does_prusa_monitor_their_github_repo_anymore/

My workaround - making a "Auto Home" routine - fits in the issue description " This change in behavior results in the printer losing track of z height slightly (its an accumulated error between prints without a power cycle) and aggressively drags the nozzle into the bed during nozzle cleaning of the Reddit poster.

RE: Core One L: "Retry" Nozzle Cleaning Routine Does Not Lower Bed — Causes Nozzle to Scratch Print Sheet

AssetXer0 — Tue, 10 Mar 2026 16:21:22 +0000

@Ruebarb,

Thank you for sharing... Your own experiences are both validating and - unfortunately - discouraging. I really hope Prusa CS and Engineering can start to take this issue seriously.

I'm sorry to hear that your replacement load cell was denied by customs... 🙄 but, I do agree with you that replacing the load cell and factory-resetting the firmware is very unlikely to resolve the issue. The firmware developers need to take responsibility, acknowledge the issue, investigate the cause, and produce a fix.

Where is @josef-prusa?: If we wanted the clear existence of damaging bugs being openly denied and instance of heavy-handed / extreme "resolutions" that don't solve the problem (i.e. firmware resets)... we'd advocate for Apple to release a 3D Printer... I say this as an Apply user replying from my Mac 😪 This is not what we have come to expect from Prusa and it makes me seriously question the direction of the company and if I can continue to trust the Prusa ecosystem.

RE:

Ruebarb — Tue, 10 Mar 2026 14:08:17 +0000

I reported this to Pursa CS 4 times in January, I could even make it repeat. The new Beta firmware 6.5.3, does nothing to address it. CS reached out to me recently and attempted to send a replacement load cell due to "microfractures". Package was rejected by customs, see if they ever get it to me. Don't believe for a moment that is the problem, as it only occurs during a specific squence of commands. The lack of problem solving ability is beyond comprehension. Or the best one yet, factory reset. They seems to suggest this every single one of their firmware issue. Even if factory reset "fixed" the issue for the moment, it is not a solution. Factory reset should never be required to fix a firmware problem. Imagine if you had to wipe your phone for every problem it had.

Here are all the known posts on this topic.

https://forum.prusa3d.com/forum/prusa-core-one-l-hardware-firmware-and-software-help/nozzle-crash-firmware-bug/#post-778788

https://forum.prusa3d.com/forum/prusa-core-one-l-hardware-firmware-and-software-help/nozzle-cleaning-failed-after-the-printbed-goes-all-the-way-to-the-bottom-to-338mm-firmware-6-5-2/#post-782329

https://github.com/prusa3d/PrusaSlicer/pull/15141