I wouldn’t call this a bug, but maybe more of a “nice to have” feature: if I render an scene with MayaSoft/ mental ray layers with Vray layers, image naming becomes a problem because the default Maya naming behavior is to add a ".’ after the <Scene> prefix to separate the frame extension. Vray renders names the file without a separator so pass_v27.0001.exr becomes pass_v270001.exr in the Vray output.
Just put a “.” in after your filename. Vray will always place the number and extension after whatever you type in. So something like
yourname_here.
will output as
yourname_here.0001.exr
cheers!