Prusa firmware 6.4.0 prompts homing and leveling failures across community

Prusa owners began reporting a range of print failures after installing firmware 6.4.0, with problems showing up in homing, mesh leveling and filament handling that in some cases stopped printers from completing jobs. Starting around January 11, multiple users flagged repeated pre-print homing and calibration failures, incorrect Z-home positions that left beds millimetres lower than expected, unload/load oddities, and sporadic parking or reload loops.

The symptoms vary between intermittent and persistent. Some machines completed an initial print and then began failing on subsequent jobs; others failed consistently and became effectively unusable for production. The failures cluster around nozzle-clean and mesh-leveling sequences and appear to affect probing order and Z reference behavior in ways that were not present under prior firmware.

Practical workarounds circulated quickly in community channels. Many users reported success by changing the start G-code to remove or modify a G28 Q line so Z-homing executes in a different order. Another temporary fix involved disabling or adjusting the heater during a leveling step to avoid triggering the fault. Where possible, reversing to a prior known-good firmware restored normal behavior for some users.

Prusa support has engaged with affected customers in cases where the vendor could reproduce symptoms. Reports indicate Prusa recommended interim workarounds, and in some situations shipped replacement cables when an electrical or cabling fault was suspected. Forum threads also show the company is developing micro-releases, labeled 6.4.1 and 6.4.2, that aim to address the issues, though no firm release dates were shared in community discussion.

This matters because firmware updates can alter motion, probing and thermal sequences that printers depend on for reliable prints. If you rely on a stable machine for time-sensitive or high-value prints, hold off on flashing to 6.4.0 or test the update on a secondary printer first. If you already upgraded and encounter problems, revert to a prior firmware when possible, apply the start G-code workaround or heater adjustment, and contact Prusa support while providing logs and a detailed failure record.

For users who tinker with start scripts and probing orders, this is a reminder that minor G-code changes can be powerful stopgaps when firmware introduces unintended behavior. Expect incremental vendor fixes and monitor official channels for micro-release announcements. In the meantime, protect important print jobs by avoiding untested upgrades and documenting any failures to help the community and support teams diagnose the root cause.