Update:
I tried removing all audio, event sheets and layouts, still not importing, that's when I realized something fishy is going on.
I tried importing 3 C2 projects that I already converted to C3 again, and they get stuck too.
I tried importing C2 sample projects, also getting stuck!
I'm trying on 2 different computers, I tried NWjs 46.4.0 and 47.1.0.
Can I somehow test back betas/stable versions to see when it broke?