As stated in title. Causes a clear border. Tracks get slightly misaligned, and color/lighting is significantly different.
How to reproduce: Start two sections of railway, building towards a central point, but make sure to start both sections from the outside, building towards center. Where they connect, it doesnt look quite right.
If you build from one side and keep going through center and out, this does not happens.
Seems to me the railway model isnt symmetrical. Or at the very least texture/lighting is different from one side to the other. If for example you are building away from you, then left and right side of track looks different.