Issue with VERIF_CRE and VERIF_MOD actions on Subcontract BOMs

SOLVED

I am calling a label (LINKDES) from the VERIF_CRE and VERIF_MOD actions to update a field on the BOM lines which is working fine for the Production BOMs and Kits, but not for the Subcontract BOMs even though the screen codes (BOH0 and BOD1) are identical.

I have tried the calling the label with a 'Case GFONBOD : When "BOMS" gosub LINKDES : Endcase' statement and also without the case statement, but neither work.

Using an infbox, I can't even get the screen to pop a simple message with the VERIF_CRE and VERIF_MOD actions for subcontract BOMs.

Is there something different about the behaviour of the subcontract windows / screens that I am not taking into account?

This is on v12 Patch 28.

Any suggestions would be most welcome.