Can confirm I’ve seen this too. Reported it before as well. When it happens, their current activity in the job assignment UI oscillates like that too.
That said, I haven’t seen this myself for a few weeks now. What version of the game are you running, and is it 32 or 64 bit?
Edit: Also – does this persist if you save and reload from your save?
Edit: Here is my original report of this behavior: Footman Promotion and Medical Attention Bugs