You can try manually rolling the version number back. You can edit the <saved-with-version> tag in the .caproj file. It should say 12000. Change it to 11900.
If you have a .capx file, you need to change the extension to .zip and unzip it first.
Keep a copy of your current file, in case this doesn't work, and you can just wait for the next version. There is no guarantee that this will work, but if you haven't use the new behaviours, as you said, then you have a good chance.
I've used this trick before, although I can't confirm 120, as I didn't install yet.