invalid lz4 chunk size??

[Joachim Lindenberg]

Hello,
when accessing one mailbox via ActiveSync / SoGo / Dovecot I get the following 
error repeatedly in dovecot log:
imap(somemail...@example.org)<1579><***>: Error: Mailbox Sent: UID=1553: 
read(compress()) failed: read() failed: lz4.read(): invalid lz4 chunk size: 
1601505441 at 16842752 (read reason=)
I can still access the mailbox via IMAP though.
What can I do to resolve the issue?
Thanks,
Joachim