Some of the overloads are buggy and wont properly stun consistently A good example of one that used to behave like that (still does?) is the first one in the Concealed Void lost sector. Unstoppable champs can also have a similar issue where the stun triggers -> they continue moving -> stun properly kicks in. One thing to watch out for is if you have multiple verb triggers going off - ie someone jolt stuns it but then an ignition triggers, at least from what I've seen recently that can knock them back into running around even though it shouldn't be cancelling it out (like Stasis does)