In my current playthrough I had Shadowheart casting Owl's Wisdom on my character to help with passive Perception checks (I hate missing things) and my party was hit with Grease. Shadowheart failed the Dexterity check and instantly lost Concentration? As far as I'm aware that is absolutely not supposed to happen as per 5e rules, which state falling Prone doesn't cause loss of Concentration - but that a DM might feel the circumstances merit a Concentration check. Even if you interpret this as applicable, surely that means a fresh Constitution check should be applied to see if Concentration is lost, not have it be instant and guaranteed? Otherwise that seems like a ridiculously powerful mechanic to be abused by players and the AI...
I feel like I’ve seen this mentioned as a bug in some thread before, perhaps by Niara? I’ll try find it.
EDIT Ah yes, here we go:
https://forums.larian.com/ubbthreads.php?ubb=showflat&Number=837531#Post837531