Okay, I was a bit optimistic before. Looking through the code and trying to reproduce the bug, I wasn't able to figure it out. If anything, it might be rare or require some very specific circumstances to occur.
I wonder if it was to do with one hero having mana and the other not? The crucible requires 10 mana to use, after all.
Otherwise, I'm sort of pulling my hair out, trying to figure this out.
Thank you for getting in touch, and if nothing else, I'll be on the lookout for it.