I've never had much success with setNewGuidValue() in a scoped app; seems like it is intended more to allow you to set an externally generated sys_id than it is to allow you to record the ID of a record. 

For catalog tasks, the only work-around I've come upon would be do something like this at the end of your catalog task script: 

workflow.scratchpad.sys_id = task.insert();

That creates the record and stores the sys_id as the script completes.

I hope this helps!

If this was helpful or correct, please be kind and remember to click appropriately!

Michael Jones - Proud member of the CloudPires team!