It appears that I have a small oil leak between the sump and case on the back of the engine. Anyone else experience this?

I know people have experienced leaks at the usual suspect places; oil cooler & lines, back accessory case, oil filter, etc. I believe this not to be the case (no pun intended).

I had both cowls off yesterday and did not detect any oil from those places but saw oil on the back 3 bolts (sump to case) and an oil run down the Aero Sport ID label and drip onto the carb heat inlet for the carb. All bolts still have the factory torque strip on them and have not moved/rotated.

Plane; EX-2, has 155 hrs on the hobbs.