Don't know if it's only affecting engineers bots or all ther other pet. You can't refresh a buff on any bots. You have to wait for the buff to expire and cast him again.
I cast the same 3 buffs on me and my bots and refreshing it 2 min before expiration time doesn't work on my bot. 2 min later all the buffs on the bot are gone and i have to buff it again, annoying.