Hi Andre, I had the same thought that there was a reason they made it read-only, but I was hoping someone could shed some light on that reason. I imagine my client is not the first customer to migrate open service orders.
The exact error I was getting is ''Error(s) occurred while writing entity record.".
Interestingly, I followed it through the tracer parser to a point where microsoft writes the error to telemetry (not sure exactly how to view these), but it does not write the error out to the infolog, or DMF. The error that writes out to telemetry is 'ExceptionWhileSettingField' on SysDataEntityPersistor.DoMapEntityFieldToDataSourceField().
I was finally able to export some test service lines and re import with my duplicated data entity, but only with all validations and business logic turned off. I am still having a hard time importing records from the legacy system, but I should be able to figure it out from this point. Once I have it all working, I will update this post with everything I did.
