When receiving in an item on an RMA, there is a "Restock?" checkbox on each line item. When I uncheck that box on any line and save, I get the super helpful "an error has occurred, please contact your administrator". Does anyone know why this would happen? I almost feel that there may be some sort of "which account do you want to impact if not restocking an item"... setting that I just haven't found??

Possibly, you haven't setup the write-off account located in Accounting Preferences > Order Management > Write off Account for Returns.

Exactly what I was looking for! Thank you