I've used w/ Win7 and now Win10 starting w/ original disc(s) and any of the patched versions (v1.0, v1.1, v1.2 & v1.2 Moks. I ran patch against downloaded GOG game which seems to work though there are many superfluous GOG files no longer used. Doubt will work if you're running on Steam or GOG Galaxy.
Make copy of current MM6 folder and rename to MM6-2.3.1 Grayface. Search for Grayface 2.3.1 patch and download into new folder then run, installing into this new folder. I use Firefox browser which asks me whether to download or run. Lots of fixes to make operate w/ Win7 and Win10 as well as commonize operation same as MM7 & MM8. Many fixes can be set back to current MM6 process (though not MM6 v1.0 version features!!!). Probably take care of your problem.