On the draw if you have both Gemstone Caverns and Devourer of Destiny (assume other pre-game effect too) then there is a classic race condition where if gemstone caverns pre-game effect resolves first and you choose the other card with a pre-game effect then the other card's effect will not trigger.

For example many many times having both Caverns and Devourer in opening hand if I exile Devourer to the caverns then 50% of the time the devourer won't trigger and the other half it will. I learned to look and see if the Devourer shows the eye to indicate it was revealed while resolving the cavern's trigger to know if I can safely exile it to the caverns and still get the devourer's trigger.

Like I said this is behaving like a classic race condition in coding. I haven't bothered to keep track of a specific example since it's been happening so long I assumed it was known until looking today. It's incredibly easy to reproduce though just have opening hands with caverns and devourer multiple times to test. What should happen is for it to always resolve both abilities regardless of which one resolves first.

I am playing on the steam version.