I was hit by this in my most recent game where I did go for a religious version the first time, but I'm not sure if it really a bug. Yerewan not being on the map, I encountered first the usual and intended behavior of losing first access to promtions you already picked "too often" before. Then at some point the choice reduced to only two or even one option, for a certain time the chaplan one (didn't reached the point of being unable to promote, though). However, after some religious fights and conversion activity which took both some of my own and foreign apostles from the map things started to normalize again. So I'm indeed convined that this is somehow tied to active apostles on the map.