I'll add it in the evening.
It seemed to me that the turn skip happened when, during my turn, while the psionic creatures were in the action queue, I opened and closed the spellbook – and the wyverns were already active. I decided to check the battle log to see how this happened, whether I had pressed "wait" or "defense." I checked for the first round – I didn't see descriptions of such actions (like the psionic creatures' attacks), and I didn't see descriptions of actions in the second round either.
I wrote this because, in my opinion, the psionic creatures were active, but after opening/closing the spellbook, they lost their turn, at least that's the impression I got.
