Seems like V-Ray RT-GPU only supports bump-mapping when using the shader-tree, means that the texture is above the V-Ray Material and switched to bump. When using the same texture and using the schematic-view and plug it into the bump-value you won't get any bump-mapping.
BumpIssue.zip

V-Ray RT-GPU also seems to struggle with the "INVERT" option for textures. The workaround is to switch the Low-Value and High-Value settings of your texture
BumpIssue.zip
V-Ray RT-GPU also seems to struggle with the "INVERT" option for textures. The workaround is to switch the Low-Value and High-Value settings of your texture