slow logins over login_trusted_network

i've upgraded dovecot on my server to 2.3.9

works properly but saslauthd that uses it for rimap authentication over 127.0.0.1 works SLOW. You need to wait 15-20 seconds before authentication.

only imap login over 127.0.0.1 is slowed down, while over any other IP is quick.

i had this problem with older version of dovecot but it was about adding login_trusted_networks = 127.0.0.1

but i already have this and logins is slow.

how to disable throttling (or better - put other limits) for 127.0.0.1?