Audi A4 Avant 2006 2.5 V6 TDI Repeated rear crankshaft oil seal leak advice please.

About 14000 to 15000 miles ago the clutch failed, which was repaired by a specialist who said that the clutch failed prematurely because of oil damage due to a failed rear crankshaft oil seal. There were no oil deposits on the drive before that I had had to put a small amount of oil in the car for the first time since the car was new. After about another 7000 miles the car started to leak oil again, leaving deposits on the drive, over night the drop would be slightly bigger than a two pence piece and the clutch started to judder quite badly. The car went back to the specialist, who inspected the car and upon removal of the gearbox discovered that oil was again leaking but this time from the gasket that forms the seal for the plate holding the crankshaft oil seal in place. After a further 7000 miles the car has now started leaking oil again, leaving similar size spots on the drive. The oil is coming from the same point on the car. So I am guessing that oil is coming from the rear crank shaft oil seal. With this engine is there any fault that can cause the crankshaft case to get pressurised putting undue strain on the seal and gasket causing them to fail. As I do not want to get the seal replaced to find it starts leaking again in 7000 miles time.

The car starts perfectly and the engine runs perfectly and returns good fuel economy, as returned over the last 11.5 years.

The car has now covered 140000 miles, had a service every 10000 miles and had a top end rebuild 2 years ago.

Are they dropping sump to get this oil seal cover replaced? If not it could be the joint to the sump leaking maybe? It could be that they haven`t dropped sump but hoping any sealant they apply to the rear seal cover is sealing to the sump. Just a thought.