Hi,

If you still need this issue resolved…..it seems to me that the error is coming from the purchase requisition connected to your RFQ line. 

It could be that the setting for ‘Convert Quotations to Purchase Orders’ was changed while you were processing the ‘PR to RFQ approval’. If so, you will not see the issue in other RFQ approvals and this would be an one off issue, only for the object in question.

Hope this helps