Valve Cover Gasket (VCG) could be your problem
When I did the OS I completely removed the dipstick and when I reassembled I replaced the O ring. That was the most difficult of the entire job. Ended up slipping o ring onto bottom of tube and as I inserted I would stop take a small allen key and tuck the o ring in. Go a little further and tuck some more. Finally I seated it by wiggling while applying downward pressure. I then did oil change just to be on the safe side. Just in case dirt went down the hole. While draining I noticed a lot of oil on the exhaust manifold and running down. Upon closer inspection I see I blew out the VCG at the back left corner. So I replaced the VCG. Now if you only changed the OS as preventive maintenance and not failure, as in my case I had oil coming out the dipstick tube, then I don't know what it would be.