Dovecot Master/Master Replication Problem

[Felix Amler]

Hi,

I've set up 2 servers with dovecot 2.2.9 using maildir using structure: 
/var/maildir/domain/localpart
Server A:    mx1.xxx.de
Server B:    mx2.xxx.de

Mails are delivered to dovecot only on server A by exim4/dovecot deliver

replication to Server B works immediatelly:
mark mail as read on server A, mail is marked as read on server B.

BUT: when i mark a mail as read on Server B, noting happens.
On Server A I get messages like this in dovecot-error.log:

2014-10-22 22:35:05 dsync-server(localpart at domain.de): Error: 
stat(/var/maildir/domain.de/localpart/.dovecot-sync.lock/tmp) failed: 
Not a directory
2014-10-22 22:35:05 dsync-server(localpart at domain.de): Error: Failed to 
access mailbox dovecot-sync.lock: Internal error occurred. Refer to 
server log for more information. [2014-10-22 22:35:05]

I googled a bit, this could habben if there is a file 
".dovecot-sync.lock" in the maildir, but I've double checked that, there 
is no such file...
Why does it work in one direction, but not in the other?

Please help

best regards
Felix