Hello,
You mention that 'most of the time, nothing happens'. What are the circumstances that permit a Vendor Return?
You may need to check settings in various module to make that you are able to do Returns to Vendors.
1. Purchase orders > settings > Purchase Orders Settings >
2. Inventory > settings > Inventory Settings
Perhaps the access group you are in does not allow for performing returns to vendors.
Kind regards,
HansaWorld Global Support