Report submitted... though as I see it this should be an easy fix (at least for this particular instance) just make the trigger for keeping your oath him not getting shoved in the pit.
Well, given that he can get shoved into the pit without your character having any chance to intervene, I think it probably should take a more active decision on the part of our paladin to not save him, rather than, eg, them just not being fast enough.
I’m not opposed in principle to the paladin’s oaths being breakable not by any intentional action of theirs but by them being just not good enough but (a) Smythin is just too hard to save, or at least he was in previous patches (particularly if you approached from up in the rafters) and (b) I don’t think this possibility is currently recognised by the dialogue options we have with the Oathbreaker Knight about why we broke our oath, which suggests instances of oathbreaking without intention are more likely to be bugs.