Oil return line fitting leak

Snugged the banjo bolt a tad and lockwired it. Ground run was dry so I took it up for a short flight  Still there. This time though it appears to hint at the metal tubing end of the fitting so I may try another repositioning and retightening. 

Off topic, but can anyone tell me if my 912UL has the thick case? Serial # 4405549

Thank You 

The compression sealing rings need to be replaced, they should not be reused.  If the leak is at the 37 degree end it suggests a nick or damage on the face.  These normally are clean and dry fit. 

Cheers

Thanks, did not remove the banjo bolt, just snugged it a bit. I’m not seeing any evidence of oil from the banjo bolt sealing ring areas anyway, I’m just trying different things at this point. I noticed when inspecting that area for the ninth time some rookie 🙄 reverse- lockwired the banjo bolt so I snugged it and lockwired it in the correct manner. I’ve inspected the face of the 37 degree nipple where the female fitting mates to it twice now and it looks as new, no scratches, no nicks, no deformity. But even so, I tried a AN conical copper sealing washer on the face of the nipple anyway, but it made no difference. 
So anyway, I repositioned the fitting, verified no oil was present after a ground run, cowled it up and went for another short flight. Post flight revealed oil once again in the same location- but less than the previous flight, about half of what is depicted in my photo above- and partially dried around its circumference. No evidence of any wet oil anywhere else on the entire engine.  Now I’m wondering since the oil only appears after a flight (my latest ground runs include 5000 rpm for a full minute and no oil appears) if I have a leak at all. Perhaps the oil source is elsewhere and the airflow under the cowl in flight deposits the oil on the fitting flat. Perhaps said oil is some leftover oil hiding somewhere from the complete oil system draining that must occur during the five year rubber replacement for my engine. I do see a trend of the amount of oil present decreasing with each flight. I ordered some dye penetrant developer, it should arrive next week. 

Circling back with an update. Went flying today with no new maintenance actions performed since last flight. Postflight analysis revealed a tiny amount of oil perched on the same fitting flat, I’d estimate just enough to darken one end of a small Q-Tip. Definitely less than the previous flight, which was less than the flight prior to that, etc.  Methinks the evidence is slowly revealing that I never had a leak.