BPCVAL does not post FRA Legislation BP Customer invoices

SUGGESTED

Using V11 Patch18.

We can individually validate BP Customer Invoices for FRA legislation customers, but when we try and use the BPCVAL function, (validate customer invoices). All we get is a Go Sub error

Unfortunately, I can't get at the more details, as the customer manually validated all the FRA invoices before we could see what the issue was.

All other legislations validate fine using BPCVAL.

Any pointers would be much appreciated.

TIA

Martin