Hi!
I think the issue happens when the game is saved to the main menu, the "continue"d.
I had the same quasi-noclip issue, but only after a game reload.
THANK YOU!!! this comment was able to help me find exactly what the problem was. I have since uploaded a new version. I'm not sure if doing this with a browser game makes you lose your save file, however, but walls SHOULD work now for everyone loading in a save in the future.