It is actually not at all random. The default texture placement (the one used when no texture placement is specified for the individual face) uses the local origin protected to the face’s plane as UV origin. V is the axis in the face’s plane closest to the local blue axis (normal * Z * normal) or in the case the face is horizontal (normal % Z == 0) the green axis (Y). U is perpendicular to V and 90 deg clockwise of it, when seen from the front side of the face (v * normal).
I often move the local axes for the purpose of texture positioning, rather than doing it face by face.
Regarding how V-Ray reads the texture placement I don’t know how it can get it differently for the different maps. Even if V-Ray read SketchUp’s default texture positioning wrong, at least the bump map and diffuse map should match internally within V-Ray. I’m suspecting the settings for the bump map of this specific V-Ray material are wrong.
@Nullo What happens if you apply the same material to another face and render that? Also, does this face lie inside a mirrored group/component? Perhaps there is a bug in V-Ray regarding mirroring and flipping of axes.