What is the LU which you are trying to create this custom field? Check whether that LU is connected to a correct module from MODULE_TAB?

You can see the module for your LU from DICTIONARY_SYS_TAB 

Thanks Rusiru.

Further scrutiny reveals that the LU PurchasePartSupplier seems to be connected to module CUSOBJ which seems incorrect to me?

How can this be corrected?

Yes, I think it should be PURCH. Not sure how this has happened. Try a full dictionary cache refresh just to make sure this is not a cache problem. If it persists then I think you would need to repair the data from this table (DICTIONARY_SYS_TAB). 

I hope this is one of your TEST environments so you can test there first. 

Hi

Im my opinion something is wrong with You dictionary cache.

Best Regards

Piotr

Update : The underlying view PURCHASE_PART_SUPPLIER has comments referencing the correct module (PURCH).  The view PURCHASE_PART_SUPPLIER_CFV references CUSOBJ. 

It looks like some corruption has happened within the dictionary cache at some point.

To correct, Is it just a case of manually amending DICTIONARY_SYS_TAB so that the LU_NAME PurchasePartSupplier associated module is PURCH rather than CUSOBJ?

You shouldn’t have to manually amend the table. You can try un-publishing and then re-publishing the custom fields on PurchasePartSupplier and then do a dictionary cache refresh.