If you are still receiving the same error and the server is crashing, the assertion failed would occur on the NetGUID.IsDynamic() check. When it returns anything other than true it halts the program operation and crashes. Given that it is the server crashing and the client remains intact, is something going on with that BP. Your client may see the BP, but it would be interacting with a non-replicated object and cause problems.
You could try breaking down the BP into smaller components and work up replication from there until you get the desired affect. It may be something specific within that BP that has a static NetGUID which is causing the crash. You can mark the components to replicate, but may have to run some other server events to make them work.
Keep working at it and you’ll get it 