To diagnose problems with Thunderbird, try the following:

Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.

I found a couple of add-ons not compatible with current release. Removing them allowed drag-and-drop of email from one folder to another to work properly.

This is a fresh install of thunderbird, but using a profile migrated from Win7. There are no add-ons installed and working in safe mode did not fix the problem.

Any further thoughts would be greatly appreciated.

Best, -Ray

Nothing comes to mind. I'm on Win 10 Pro and have been on it for years. I suppose it's possible there is something in the Win 7 profile that's interferring but seems unlikely. Best of luck.

/steve

Thanks for your reply. I wish there was an easy way to fix it, but I appreciate your efforts nonetheless.

Best, -Ray

I have the same problem and restarting with add-ons disabled does not resolve it. No changes have been made to Thunderbird since the error started. Any suggestions?

I'm still having the same problems as well. email duplicates itself back to the original position. No obvious solution.