hi @enething1 , @Hardcawcanary ,
Just checked the UEFN 5.6 source code at the failing location and this is the message
// Updates the suffix to be given to the next newly-created unnamed object.
Basically you have an asset/object that is not named/saved correctly.
The possible actions and run Validation Run Validation fixer check that the new asset conforms to the power of 2.
Validation and Fix-Up Tool | Unreal Editor for Fortnite Documentation | Epic Developer Community
Perhaps go back using UEFN revision control and undo the last changes