Cached message size smaller than expected

Greetings,

Can anyone help me to solve this problem?

When doveadm sync is running nightly, we have a certain user's mailbox that will not properly sync and the logs give me this error (user private info redacted):

Error: Mailbox USER/MAILBOX: UID=79: read(/vmail/domain.org/user/.MAILBOX/cur/1575914253.M611834P7822.triata4,S=41893,W=42718:2,Sc) failed: Cached message size smaller than expected (41893 < 41897, box=USER/MAILBOX, UID=79) (read reason=mail stream)

I have deleted the dovecot indexes in the synced backup of this mailbox, as well as in the actual user's mailbox itself and I'm still getting this error.

What am I missing?

Thank you for your help here.

-Asai