Hi Nick!
I got curious when you said that you couldn't reproduce the problem so I tried to do the same in another folder, and I was unable to reproduce the problem as well. After spending some time in my main project, removing lines to narrow down the problem, I managed to get my main project to work with the repl! I'm still not sure what broke and why, but it seems it got fixed when I removed the elm-stuff folder. I suppose there were some cache somewhere screwing with the repl :/
Thank you all for trying to help!