Hi there! We are using Forbidden Magic in Combination with a custom generated Nether (FWG)
and we werent able to get any FM Shards from Mobs so far. So our Question ist , is your Mod Checking for Dim -1 ? And if so how can we work around this?

Yes, it's specifically checking for Dim -1. No idea how you'd work around it other than adding some custom recipes.