Hey guys,
I tested that file in 4.2.1 and it works fine (the same as in 4.0 for instance). Maybe it helps if you change the Viewport Pixel Size from Automatic to 1x:

Although I don’t think that’s the problem.
We have seen discrepancies between Blender Versions before that ‘worked inconsistently’ on different systems (so far unsolved).
You might also try Downloading Blender from Blender.org, instead of through Steam…