The general trigger is: you enter conversation with a companion, but the conversation then switches to the PC and requires a roll by the PC.
There might be other triggers/situations, but that one always causes problems.
This is not only a bug, but a gameplay issue also - you can't use companion skills in some situations, so your PC has to have all of the critical skills instead, no matter how you want to play them.
[edit] [just got beat to this point by the prior post; consider mine a confirmation]
Last edited by RBarbare; 04/12/20 11:34 PM.