I owned a 944 for a couple of years back in my (much) younger days. Took it into the Porsche dealer to have a service and two weeks later I noticed a pool of oil on the garage floor. I checked the oil level and was horrified to notice it was well over the high mark on the dipstick. I called the dealer and explained to the service manager that I had a rear crankshaft oil leak and asked if overfilling it with oil could have caused the problem, to which he replied that overfilling puts lots of extra pressure on engine seals and most certainly did cause it to blow the seal. He wasn't so happy when I told him that they had just serviced it and overfilled it and therefore I was holding them liable for repairing the leak. They did agree to replace the faulty seal and filled it to the correct level once finished