What brand filter are you using. Is the drain plug on your oil pan a 17mm hex bolt head or is it a 14mm allen type. Otherwise you may have the latest M130 oil pan which uses the 13mm hex bolt head drain plug. In this case you will use a small crush washer and not use the larger one. Most important is to make sure that the inner upper seal is still hanging on the neck in the filter housing. If this is gone your engine oil is not being filtered.
I did some work for an authorized MB dealer last week. The dealership had been in the family since 1968.The owner of the dealership had a very nice collection of vintage Mercedes cars. His cars were always serviced in their shop. Well, I checked the filter housing, guess what? The upper filter seal was gone. It's very important to check for this part. It is often missing, no mater who serviced or owned the cars.
Some replacement oil filter brands are 3mm shorter than the original oil filters and will not seal to filter the oil. There is usually not any felt washers with the oil filter. I am wondering if you have a fuel filter?