Warning: Failed to do incremental sync

[Ivo]

I am getting a lot of these messages (on the master side of replication)  :
dovecot: doveadm: Error: dsync-remote(userxyz): Warning: Failed to do 
incremental sync for mailbox INBOX, retry with a full sync (Modseq 81589 
no longer in transaction log)

Having "Error" and "Warning" on the same line is confusing, to start with.
If I get it right. it means that very often (incremental) sync fails and 
replication starts again after 5 min  but this time by doing full sync, 
which, I guess, is not good (more resources used).
Since I am doing only one way replication what could be the reason for 
those errors/warnings? Nothing is changing files on the remote side 
besides dsync-server.
Is there anything I can do to "fix" this ?


# dovecot --version
2.2.33.2 (d6601f4ec)