On 27 Mar 2019, at 14.58, Timo Sirainen via dovecot <dovecot@dovecot.org> wrote:

dovecot isn't able to auto fix the indexes and manual deletion is
required in all such cases

So if it keeps repeating, it's very strange. Could you send me such broken dovecot.index and dovecot.index.log files (without dovecot.index.cache)? They shouldn't contain anything sensitive (only message flags).

Tested with the index files you sent. It gets fixed automatically in my tests.

The backtrace shows that after fsck it fails to write the fixed index to the disk, because mail_index_write() fails for some reason. Except there's no error logged about it, which is rather weird. Do you still have the lmtp core? Could you do:

fr 9

p *log.index