Do you one better, I got a video of it.
...
Grabbing at straws a little here, but you haven't by any chance ended up with the cap not on in the correct orientation, have you (can you)?? Or maybe you've put a screw in that position that's too long for the hole in the housing just there so that it
seems to tighten down but doesn't really? Or could it be that there's some crud (old locktite maybe??) that's been pushed down into the bottom of that screw hole that's now being compressed when you tighten the screw down and stopping the screw from tightening down/going in far enough to tighten the cap properly??
If it's not something like that, then going by the vid, I'd be leaning back toward it being the cap itself no longer being square so that it won't seal; the mating surfaces no longer being properly flat so that they won't mate together evenly/properly (see my earlier comment re 'lightly oiled glass' to test that); or somehow, there
IS a nick or scratch in one of the surfaces just there or maybe in the O-ring or O-ring groove that's just too small for you to see with your naked eye, but it's a big enough nick to to let that much oil out!
There's clearly gotta be
SOME reason for it to leak oil like that, so even if you
think that it can't be one of the many options that've been suggested &/or looked at/tried already, maybe you need to re-visit and step back thru them all again to see if you've missed anything?!
It
IS frustrating & weird I know, but there's
gotta be a reason for this oil leak, and there's really only a limited number of possibilities. You just hafta accept that it
IS one of them and then troubleshoot it to work out how to narrow it down to the real culprit - or you could pay someone else to do the same troubleshooting job, only they generally charge like wounded bulls -
IF they'll even take on the job of trying to troubleshoot anything like that in the first place!
Ps: Just another thoughty, have you checked to make sure that the filter is inserted and mounted properly?? And/or that any old gasket or clear plastic seal, etc that might've been used to keep the new filter clean before installing ended up being removed properly?? IIRC, there have been a couple of instances reported here where the old gasket or O-ring was left in there; or the filter was either wrong or inserted wrong.
I know these are probably long shots, but sometimes, these odd things slip thru and cause all sorts of difficulties!! I had a fella bring his diesel engined Nissan Patrol around for me to check out a while back cos it was seriously down on power after he'd only serviced his air filter... It made much better power once I found and removed the old rag that he'd used to make sure the filter housing was clean before putting the new filter in - and then forgot to take out before putting the cover back on!!

Sometimes, these sorta things just slip thru!
