What I can say so far is that Anon and Mega and Mix have identical content (Racity is only at 50%, can check it later), so whatever is the problem on your PC, it's not depending on Mixload.
I don't know what these versions are based on (Steam, itch, ...), but the .exe file differs from my Gamejolt version in two small sections, all the rest is equal. My best guess is that in these two sections the access to steam.dll or something similar happens, since I checked the file and my AV didn't find anything suspicious.
If you are unhappy with the download options, I suggest buying the game on itch.io or - if you get off on DRM, censorship and seprated DLCS - on Steam. It's not that expensive.