MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking  

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

From the GitHub issue:

FYI: The fix will be included in the next firmware release. Please understand that testing of new firmware takes a while. The MMU can be used on the MK3.5/S, MK3.9/S, MK4/S, CoreOne and CoreOne L so testing all these possible combinations takes a while.

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

This is still happening in 2026.  Glad I found this post.  Will try and downgrade to the earlier FW.  I wish I could get the filament back that I've wasted trying to get this print to complete.

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

Posted by: @dbv

From the GitHub issue:

FYI: The fix will be included in the next firmware release. Please understand that testing of new firmware takes a while. The MMU can be used on the MK3.5/S, MK3.9/S, MK4/S, CoreOne and CoreOne L so testing all these possible combinations takes a while.

That posting was from months ago with no indication of when to expect a new release.

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

Glad I found this… I’ve been having the same issues and its been driving me mad.

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

So I hate being the new guy and ask a question that’s probably been asked a thousand times before…but I’m not having much luck searching for an answer.

How do I change my firmware BACK to an earlier version as some of you guys have recommended?

RE:

@martinij77
Here is a help doc that should give you the info you are looking for;

https://help.prusa3d.com/article/how-to-downgrade-firmware-core-one-mk4-s-mk3-9-s-mk3-5-s-xl_725930

RE: MK4S +MMU3 + 6.40 Alpha FW - Stuck at Reloading Filament - 99% Parking

Thanks Dude!