I tested and I'm having the same problems.
It almost looks like Displacement expands the UV slightly. Setting the scale of the texture to 1.005 gets rid of the weird borders.
It's also notable that the Displacement seems to ignore the Border modes, and only uses "Wrap Around". If you could set it to Mirror it could work (not removing the problem, but the symptom..).
The left one is "normal" (Scale 1.0 etc) Displacement, showing problematic borders. The right one shows the same texture, scaled down to 0.8, with Border Mode set to "Black Color" (for visualization), so the black areas should be flat (and lower than the rest), which they aren't.
BTW, I exported it to an ORBX an tested in SA, and with the same issues..
(2018.1 RC6 / v17.5 [also tested in 2019.1 XB1 Standalone])
Windows 10 Pro - AMD Ryzen 7 2100X 8 core 3.70GHz - 32GB RAM - GeForce GTX 1080 8GB
Octane Prime - Blender Plugin user