I had a defective oil filter once (Purolator) that would not seal. Didn't seem to matter how tight I got it. Finally replaced it with a Fram, and the leak stopped. After removal, it wasn't obvious to me what was wrong with the Purolator filter or why it was leaking, but it was the 3rd time I've had trouble with their filters and don't use them any more.
So long story short, don't overlook the possibility of a defective filter.
2013 GT Premium Brembo
MGW, Blow Fish, AM Hood Struts
Tinted, Borla Touring AB, ProCal Tune
Full Shelby/Kicker Audio Upgrade