I had a very well fed flame angel in a 120 that was a model citizen for several years.
It started slowly with trachys and Caulastrea, then all my LPS and zoas were suffering. I was slow to recognize it was the flame since he had been so good for so long. One day I caught him red handed ripping hunks of tissue off my favorite open brain.
I think its not if, but when. I noticed that LPS were the primary target of my flame angel, and I am sure he was eating some zoas as well.
One of my favorite fish but not worth it IMO/IME.
Best of luck