Cheers,
this happened to me several times now. As I try to complete the heroic quests and pushing them to 100%, the games freezes when I destroy an opponents support. Most of them start with a support on field, especially in the later stages, and it’s nearly impossible to win against some of them without destroying their supports.
As sidenote: this didn’t happen in some earlier versions of the game. It must be a fairly new bug then.
Thanks for your support.