Separate Render Channel - saved files are wrong

[Mnietek2707]

V-Ray GPU, NVIDIA Denoiser is ON with upscaler.
Latest V-Ray version.

Working with V-Ray became really annoying. Just saving file - is this really that hard task?

MultiMatte Element

V-Ray Frame Buffer


Saved file - on ther right is white part for some reason:

[hermit.crab]

Could you attach (or send) the scene so we can take a look?

EDIT: Also, what kind of image format are you outputting to? If you're saving .jpgs, does it happen with .pngs?