Suddenly hiding anthia

[Coasting]

You could try pulling him and his buddy out into QT (lots of hidey holes would keep him calmer i think) and running a round of Prazi or something and keeping a close eye.
But I know their a Pita to catch....
I would change up the environment somehow and see if that does anything. Could very well be something we dont notice.
Do you garlic soak the food?
Tried other varieties?

Anthias can be very odd fish at times.