Did it happen more than once?
If so, does it happen:
with every material
in a similar location
When it is actively cutting material
with the burr embedded in material
with the burr just hanging out in free space
The sensor is likely picking up an overamperage trying to turn the burr or a lower spinrate than it should have and thinks the burr has stuck.
Someone will likely have a great answer, but it ain't me. Just want to give you the best chance of getting a good answer by getting some more troubleshooting info.
Edit: you've been having lots of trouble withnthat mill lately. Ever get it to a fixin'n people place?
https://dentallabnetwork.com/forums/threads/roland-dwx50.29244/post-297577