Here's something you can try if you're too lazy to backup the things you want and reinstall the old game.
Install FH someplace ELSE when you run the installer, an example would be if you made a path like this
C:\FeralHeartTEMP
And then install the game there, this would mean you would have 2 games on the C: drive just one of them would be a new working version. The option of where you want to install FH ALWAYS shows up, so don't be in a rush and make sure you don't overwrite the old game since that's not what you want.
Since I assume there's a problem with the masking for all the models and not just one preset or character, go into C:\FeralHeart\media (old mask faulty game)
inside of it there's the folder "textures" which holds the textures for all the canine/feline models but also things like ingame buttons and other hud. CUT the folder(Do not copy) onto your desktop for now just in case the game acts weird later on.
When you have placed the old textures folder on your desktop, and your old game is without a textures folder, go into
C:\FeralHeartTEMP\media that you just installed, copy that textures folder ther, and then paste it into
C:\FeralHeart\media
If you did this right the game shouldn't even ask you to overwrite anything.
Now try to run the game and see if the old masks show up correctly.
If this somehow fails and you still rather want the old ones back, just cut out the folder as before or remove it, then copy the one still laying on your desktop and paste it back in where it used to be. In general though, this folder should not affect any custom maps, presets, items etc. Since the mats and images lays(should lay) elsewhere.
Should work for you. And once you have tried out the old game and it works fine you can just remove the whole "FeralHeartTEMP" game/folder comepletely from your C drive.