I tried to export issues via "repository settings" > "Issues: Import & export"
I clicked on "Start export" and a pop-up shows and starts the export process.
Sometimes this fails, and the pop-up then says "Unexpected error"

Sometimes it works but the link it created (and also sent via email) goes to:
https://bitbucket.org/!api/1.0/repositories/[WORKSPACE]/[REPO]/issues/export/zip
which never works, and shows the standard "Something went wrong" screen.

I've tried this several times in the past couple of days. Any idea what had gone wrong?