Hi Isabelxxx ! Thanks for reporting!
I believe the issue has been resolved for now. The export function should now work perfectly
Regarding importing, you can currently import playlists with up to 50 tracks. For larger playlists, there are some rate limit issues that will be resolved within the next 2-3 days.
You are right, latest commits seem to have fixed this issue, so closing it.
It seems lately development has not been reflected on some of the open tickets.