Dry Season No eruption

It happens occasionally. Idk if it's a bug or not, but the same thing happened to me. 

I have the same issue. Although for my save the eruptions only miss out when I dont play the whole dry season in one session. I basically have to play the transition from monsoon to dry and then dont exit the game for the whole season. If the world gets reloaded for whatever reason (Seaworthy/Enter-Exit Volcano, save, exit and reload the save file) the Volcano eruptions dont happen anymore until one year passes.