Firefox 52.7.3esr, Windows 10 pro
I had a backup from 4/23/18. But I just today did a password change and discovered that currently I can't export using v4.21 and previous versions back to v4.16.
At that point I installed v3.5.23, imported the 4/23/18 backup, updated the password, and then was able to export it normally.
Sorry, my mistake. The
Sorry, my mistake. The problem was caused by Ninja Download Manager.