Bevel box / Transfer unit oil leak

[Fordy]

Just had an inspection service carried on my 2017 S3 32,000 miles at the dealership and was sent an Audi cam video showing me that they had spotted oil leaking from the bevel box / transfer unit and they wanted £321.00 to investigate, I kindly pointed out to them the car was bought from another Audi dealership and was still under extended warranty under the approved used scheme and that I would of thought oil leaking from a transfer box would be covered under said warranty, was told they would have to determine where the oil was leaking before being able to put a claim in against the warranty, so the car was kept at the dealership for investigation, the next day I get a call to say they couldn’t determine where the oil was leaking from so have cleaned the leaked oil and asked me to do another 500 miles and then return the car to them for re-inspection. I feel I’m being fobbed off a little by them and wondered has any one else had problems with the bevel box transfer unit leaking oil ?