Thanks for the feedback. I'll probably need to add some logging to determine what is going on. The encounter keeps a list of people that are locked to it and this should not include pets. When the mob dies, we check the number of people locked to the encounter and make sure its less than or equal to the shorthanded value.
Somewhere this must be failing. I'll try to get the additional logging hotfixed later this week so we can see what is going on.
LINK