6.4.0-RC Firmware for Prusa MK4S
Summary
- New features
- Nozzle cleaning failed wizard
- Fixes
- Fix #4816
This is the release candidate for the upcoming firmware 6.4.0 for the Prusa CORE One, MK4S, MK4, MK3.9S and MK3.9. It reunifies the firmware development branch after the temporary split during the CORE One launch, where 6.3.x was released exclusively for CORE One and other printers remained on 6.2.x – along with bringing new features, improvements, and fixes across all platforms.
Builds for XL, MINI, MK3.5S and MK3.5 are temporarily not included due to identified issues currently under investigation.
For a complete overview of features introduced in firmware 6.4.0, users can refer to the 6.4.0-alpha release notes published earlier.
Nozzle cleaning failed wizard
The recovery process for failed nozzle cleaning has been reworked into a new step-by-step wizard. It replaces the previous purge option introduced in 6.4.0-alpha.
The wizard also includes a filament retraction step to prevent oozing before retrying the automatic cleaning sequence, increasing the chance of successful recovery.
Release notes:
https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.4.0-RC
RE:
The bugs from Alpha are still present in this RC.
MK4S/MMU3
RE: 6.4.0-RC Firmware for Prusa MK4S
I confirm that as of September 27, 2025, the error: Stuck at Reloading Filament - 99% Parking is still present. It disappeared when I reverted to version 6.2.6-RC. I don't dare revert to this version of September 23.
RE: 6.4.0-RC Firmware for Prusa MK4S
I've updated fw today and i now get the "Stuck at Reloading Filament" "Parking"
Just thought i'd inform you of this,
i will be reverting back now,
Thanks,
Scott.