Dovecot 2.2.31 Incorrect Search

[Siarhei Chystsiakou]

Hi.
I have installed dovecot 2.2.31 and fts plugin with Apache Solr 6.6.1.
I have found that imap search is not correct in my dovecot. For example, I
want to find  email from user s.chistiakov at example.com. I run IMAP command
"SEARCH FROM s.chi" and result is null. But if I run IMAP command "SEARCH
FROM s.chistiakov" I get list of emails from this user.  Why does this
happen and how to fix it?
Help me please )
Thanks.

Result of my actions in telnet: https://hastebin.com/fewanacafu.md
Dovecot config: https://hastebin.com/noqehimaxu.makefile