Blender Version: The official release for 2.80
Short description of error:
The options menu for blendshapes allows us to create a "new shape from mix". The expected behavior is to generate a shape that will look as the mix of the blendshapes active when the function is triggered.
A very convenient part of this was that the vertex masks utilized on the active blendshapes were taken into account when baking into a "new shape from mix". This new generated shape would therefore not present any masked parts from the previously mixed blendshapes. Unfortunately, this no longer is the case, and baking shapes from shapes that have been masked, completely ignores the masks utilized on the active shapes.
This way of masking shapes was a very neat thing we could do and I hope it hasn't been taken out intentionally, as it was a huge timesaver for blendshape artists.
Amazing work on Blender, regardless. Thank you for your work.