Interesting, this looks like a connector bug, but I found another dev forum post for a similar issue - Webservice - No configuration found for 'Add Entitlement-underfined.
This user was able to fix their issue by updating their ‘Add Entitlement’ operation type to match the one shown in the error. So in your case you would do a full source update through the API and update the operation type to ‘Add Entitlement-’. Feels like a hacky fix though, maybe reaching out to SailPoint support or re-creating the source would be a good idea as well.
Thanks!
Liam