it seems that when i set normal map to tangent space and apply a normal map to a surface its either on or off and the bump multiplyer no longer works. I can switch to normal map in object space and the multiplier seems to work again but there is no explanation of the differenaces between object space and tangent space so i do not know if this is correct or not?
I have looked into this problem and it seems to be happening only with nightly build, but not with stable builds. Are you also reproducing the problem with nightly or stable build? I will have further look into the problem and report it for fixing.
The issue seems to be fixed with the latest V-Ray 5 stable builds. Please if possible download and check if it works for you and if the problems still persists we will have a further look into it.