Permissions to Merge Assets

Hi,

after upgrading from 7.1 to 7.5 my customer is not able to merge assets anymore.

"Merge failed.The caller ('USERNAME') does not have one or more of the specified permissions on the specified items."
 
Nothing in the logs. :(

How can this error be debugged, if nothing is in the logs? (The same btw if the customer adds an asset to an organizational group)
When I do it with Symantec Administrator permissions it works, of course.

I appreciate any help on this!

Best regards,

Andreas