New mail in Inbox is auto-shifted to Junk when opened/closed

[thoste]

Since a while I noticed a strange behavior on some messages.

Occasionally when I open a new, unread message in my Inbox it is successfully shown in message pane.

But as soon as I close this sub window the message is automatically (!) shifted to my Junk folder.

I have to open the "Junk" folder and the critical message and manually click on "NOT Junk" button to get it back to Inbox.
Once it is back it is stable (=not shifted again to "Junk" folder). It is NOT a junk.
None of these message are Junk. I never changed my Junk settings.
Moreover if TB thinks that it is Junk it should put the message immediately to "Junk" folder and not into Inbox first.

It happens to approx 5% of all my incoming emails and is not re-producible.
I am using 64bit TB v102.3.1 under Windows 10
But as far as I remember this bug happens in previous versions too.

Everything else works in my TB installation.

This should be investigated.
Its clearly a bug.

[DanRaisch]

Moving to Thunderbird Support as no specific bug has yet been identified here.