Hello! Probably it is not bug but I see it as unreasoned detail that should be fixed.

For some reason, the vexes does not considered as raid mobs and so raid ends after all raiders are killed but not vexes. It creates the problem - when player finishing raid he may be killed by vexes (on 7th wave very many vexes) and so effect Hero of the Village disappears. I think it is not so good because player should feel safe after the end of the raid but he does not.