Kmail - LLCONFLICT

Hallo KDE-Discuss-Community!

Does anybody know, what is a [LLCONFLICT] in Kmail (or akonadi) and how I can handle with?

Since a couple of days I always get follow error message, when I send an email - independent from the account type (imap or POP3).

Sending the email failed
The result cannot be saved in the object. 
[LLCONFLICT] Resource akonadi_imap_resource_3 tries to 
modify item 178593 (7665) (in collection 3815) with revision 1;
the item was modified elsewhere and has revision 2, aborting STORE. 

But the email was sent and received by addressee. The only real issue, I can see, is that the sent mail is marked as unread, even if it is a sent message.

Something very similar I’ve found here:
Bug 454094

Thanks in advance for help