Hmm, you may be right about this being the influence of multiple light sources rather than a normal-map issue. Sunlight in particular can have some unexpected influences it seems, including on block faces which should not be able to receive direct sunlight. I tried some tests in a void sector as well but blocks were still sunlit? Enabling shadows did not change the effects either.

I'll try to play around with it some more in different scenarios. In my example on a station, the affected face was basically opposite the local star, i.e. the face that is mostly in shadow (not using the shadows option, but meaning that face is not actively lit by the star). What really struck me was observing how the lighting cues changed when I moved around the face. For example when viewing the horizontal pipe side, when I moved "up" the specular highlights moved "down" and vice-versa, indicating that the pipe was concave. On other facings the cues moved as expected for a convex pipe.

I should note that the version tested was specifically build 20160522_114626.

Apparently the trick to reproducing this is that the unmanned ship NOT have a faction. When I had encountered this, I was sending a basic stick ship (with no faction module or tag) toward a pickup point and pickup rail on a factioned station. Under those circumstances it gets stuck on the pickup rail until reloading (this was in single-player).