OK. So we are back to how the relationship is defined. This would likely be defined as a BREL. I understand you don't have access but the person who defined the object in Service Desk must have the appropriate access.
We need to see this information. To get this information someone needs to open a command prompt on the Service Desk server and use the following 2 commands to reveal the definition:
bop_sinfo -d cr > definition.txt
bop_sinfo -d custom_table_name >> definition.txt
and post the contents of definition.txt here.