If on the Frozen Scythe Mending gets added in an anvil it corrupts/crashes the game. If the items stay in there because of a mod and it's an auto anvil, every restart won't help and the chunk gets corrupted.

Fabric 1.19.2 1.42.1

There is no weapon in Simply Swords called Frozen Scythe?

I'm assuming you've gotten this mixed up with another mod, so I'm going to close the ticket.
If I'm wrong, please feel free to reply with further detail of the issue.