There could be a couple of issues here to check. The Design Synopsis that @pstr mentions should work, unless it is corruption or duplicated design element.
First try using the search in designer, rather then form itself.
Search for "CONTACT_NOMINATION" and "PartnerContact".
This will display the results in DXL format, so you can check the source, or manually go to the related objects yourself.
another option is to right click on the related design element and "Edit with DXL". It will allow you to see any corruption, for example fields which are not rendering in the UI.
Lastly you can try using NotesPeek as it can easily check for design duplication. You can pick it up at the following link.
http://www-01.ibm.com/support/docview.wss?uid=swg24005686