Most likely the alignment tabs inside the valve covers are heat cycled deformed. They are located on the exhaust side of the valve cover. Need to carefully pry on the corner closest to the alternator. When you do get the valve cover off, make sure you remove the 3 tabs inside the valve cover or you will never get the cover to seat. Another BMW gotcha! Also you have to remove the fuel rail to get the drivers side valve cover to clear the Valvetronic sensor. Be careful cause that sensor is 300 dollars! You need to rotate the steering wheel with the universal joint union bolt clocked properly to remove the drivers side cover. Do not ever force anything! This is a level 8 repair as far as mechanic skill, it is the most difficult valve cover gasket I have ever repaired! Oil pools in the rear lower corner of the cover, need sealer in that corner as well as the half moons.