As was mentioned yesterday, it’s an indication of fear.
It could come from several places. Inability to do the job is certainly one. But there could be others.
Yes, fear does that, and more besides. I can give you first-hand stories of what fear on the job does to co-workers and supervisors. In my case, they weren’t happy until I was forced out. What they did over a five year period was make CFIDS/ME much worse than it should have been, and all the while, they thought I was faking being sick. So they put on more pressure.
Fear of a co-worker is ugly.