Vray maya bake issues:
1. Sometimes if you are attempting to press bake in vray maya, it will do NOTHING, no messages in the script editor etc. zip nada. Closing your render window will fix this.
2. When creating the bake set for vray maya it may give a value is out of range when you select your bake options set. Closing the open hypershade fixed this.
3. When attempting to bake a large thin box in vray maya, it may bake black, this appears to be a bug. baking instead onto a plane should work. This is especially insidious because it may actually RENDER your bake from some angles, but appear black from others!
These issues have been observed in maya 2017 update 5 and vray next 4.3