If there is one that seals around the screw either A) they did not replace it or B) they did replace it and nicked it with the threads which is allowing the oil out or C) it is offshore made crap-as in the tolerances are loosey goosey-more than likely the last one. You may be able
To double up on the gasket or try wrapping Teflon tape around it and see what happens.
mike
Upon closer inspection it would appear that the old washer just fell apart (probably the screw/nut was tightened down enough to FUNAR it). I have replaced the old washer ) what was left of it) with a new one and the problem has been corrected.