Same here … (Windows)
Combine Textures works fine on vertical and horizontal faces in SU 2016.
In SU 2017, Combine Textures fails on vertical faces, but works as expected on horizontal faces.
@Bryceosaurus This appears to be a Bug / Regression in 2017
Here’s the SU 2016 example model referenced in post #10 above.
Combine Textures.skp (138.8 KB)