Ive not seen a high pressure switch become defective and leak. Possibly the o-ring that seals the switch to the dryer is leaking. On the other hand I have seen the low pressre switch on the dryer actually leak out of the switch. Typically both switches get replaced at the same time.Depending on when you had the repairs done the parts may still be in waranty. Most MB parts carry a 12 month/ unlimited mileage waranty.
Mercedes Benz Master Tech