Somehow I can’t reproduce this here on OS X but I never use the master section or have to save/load master section presets. For a workaround, does it work if you fold and unfold the plugin GUI? This often clears up GUI issues. Do you get the issue if you load a new instance?
I would write to Dave @ DMG, he’s usually very responsive.
Here is a GIF of two things to try. The second option in the GIF is what I mean about folding and unfolding the entire GUI window:
