Hey

How long does it say exporting playlists for? It could just be taking a while to write to the file for that many tracks.

Do you get the same issue if you just export a single playlist? How long does it say 'Exporting playlist' for if you do that?

Thanks for raising the issue with shift selecting, that looks like a bug that's come up in the latest version. I've added an idea to the roadmap to get this fixed:

https://support.mixo.dj/t/2271-shift-select-not-working