@dc42 Thanks for your follow-up.
Forgive me, I thought our client was using a Duet3 6HC, but rather was using a Duet3 Mini with the 2209 TMCs.
Two motor have burned so far, and we are trying to find the source of the problem before going further.
The 5V comes from the Duet.
Only the extruder is affected.
The first motor was set to 0.365A RMS, the second motor was set to 0.5A RMS.
The second motor never over-heated like the first one did.
