Can't complete boot after startup following faulty firmware upgrade

[puris 0]

Hi everyone,

I have been running 3 Ultimakers in a small shop for about 3 months now with few to no issues.

With the recent firmware release (12/04), I upgraded the firmware for all three. However, one of them, the one that's been in use the longest, has an unusual boot issue.

After the firmware upgrade process completes the first part and it reboots, the printer is stuck with "Ultimaker" on the screen, the dial light on, and the frame lights on at full brightness.

A power cycle does nothing, but a power cycle waiting 10+ seconds allows it to boot seemingly normally. In this state, network prints fail, the Cura web panel for the printer unable to show current printer sensor status.

I have tried redoing the firmware update manually with a USB using 4.1.4 (12/04) and 4.0.1 but to no avail.

I pulled the USB logs, there's some stuff about being unable to access the motion controller and other things but I'm not sure how that's exactly related.

I'm all out of ideas, so I'm hoping someone out there might be able to lend a helping hand.