PVZ Heroes Softlock caused by Wizard Gargantuan + Graveyard interaction

PVZ heroes softlock

I was playing Super Brainz and playing a homemade deck that contained the Graveyard environment and Wizard Gargantuar. I tried placing him into the Graveyard and this did make a gravestone that contained the WG, but the game softlocked after this. 

My theory is that the Wizard Garg's ability is trying to activate, but the gravestone is not allowing it to do so, preventing the game from progressing. i havent experienced this with any other zombie "on play" abilities so far. only the Wizard Garg. Which is a shame, i think a sneaky WG deck could be fun to play around with.