Oil return line fitting leak

Completed my first five year rubber replacement two weeks ago on my 200 hour, 2018 912UL and no good-intentioned maintenance action goes unpunished. Been fighting a persistent oil return line fitting leak ever since. I have the Rotax p.n. 956050 Hose Nipple 16 under the engine secured by the Rotax p.n. 940879 Banjo Bolt M16x1.5. Eaton steel AN8 fittings at each end of the return hose to the oil tank. The leaking oil appears on the Eaton hose fitting under the engine. A small amount of oil (one or two drops) will be evident on the bottom flat of the Eaton hose-to-nipple AN fitting after an engine ground run (well, most, but not every, engine ground run) or following every short flight (four short flights), doesn’t leak static, and I can’t determine visually where the source of the oil is located. What I see every time after a flight (I’ve wiped the connector clean on every preflight) is a small bit of oil dangling from the middle of the Eaton connector (where one would place their wrench to tighten the connector) with no visible trace of oil anywhere else. Tried swapping the hose ends to see if the leak moved up to the oil tank. It did not- both connectors will have oil on the connector flat if attached to the steel nipple under the engine. Never any leaks up top at the tank from either hose end. Tried a copper AN8 connector crush fitting, didn’t help. Ordered two new steel Eaton fittings and built a second new hose, didn’t help. Might try oil leak dye but my past experience with that stuff is that it’s a waste of time and money. With oil hanging from the Eaton hose connector, I’ve swabbed the connector at the thread end and the tubing end with a q-tip, and it comes up clean and dry. I’ve searched everywhere under the engine with a good light for any oil coming from anywhere and find nothing. I could next replace the steel nipple, but 1. It looks perfect, no scratches or damage anywhere, and 2. A new one will cost $160. Any suggestions?