I recently used the Version Utility to upgrade a project from 7.3 to 2020.1.

Surprisingly no errors, no code changes required (for this solution anyway) and everything compiles and runs.

However I have an issue where the UltraDockManager keeps complaining about:

The 'AllowDrop' property is set to true but the ApartmentState of the current thread does not support drag drop. To disable drag drop functionality set the 'AllowDrop' property to false. To enable drag drop functionality you must set the ApartmentState of the thread to STAThread. This can also be accomplished by putting the [STAThread] attribute on your 'Main' method.

I have checked, my Main method does have the [STAThread] attribute and when I comment out every appearance of AllowDrop = true or set it to false, this message continues to appear.

If I dismiss this message, everything seems to still work with the toolbars:

1) Buttons work
2) I can move panels around
3) As I launch new forms that add/remove stuff from the toolbar, all that seems to work.

The solution is far to large and proprietary to send and I have no idea how one would reproduce this error (since it happened after upgrading).  Any ideas as to why this keeps popping up and how to fix it or disable this message?