Let's see if I have this straight. You did not list an origination fee on the initial LE. Later it was noticed that the seller had agreed to pay for an origination fee, if there was one. So, you want to add an origination fee to the loan so that the seller pays for it?
Well, outside of the UDAAP and fair lending implications - sure, why not
Or you always charge an origination fee and actually had a copy of the purchase contract in hand at that time and treated this as a specific seller credit when you issued the initial LE?