archangel leaving way to early

I was raiding the chasm, had pretty fresh conjurations, and a couple of rounds into it the angel just leaves. I still had about 32 hours on the conjure with a 23 charisma. The only answers I can come up with are: The archmage dismissed it, Kungkruk had some special power to get rid of it, or a buggy timer? Some other things of interest: Kungkruk was the only defender, I was raiding with Thenrek and he rescued me a couple of times. That's about all I can think of, it was just very very odd that it stayed less than half it's usual time.