invalid lz4 chunk size??

Hello, when accessing one mailbox via ActiveSync / SoGo / Dovecot I get the following error repeatedly in dovecot log: imap(somemailbox@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