My main.cf config for antispam

[kiribool]

Hello all,

i'm using drweb for antispam. Daemon of drweb binding to localhost:8025.
Configuration of drweb within postfix:
main.cf
content_filter = scan:127.0.0.1:8025
receive_override_options = no_address_mappings
master.cf
scan unix - - n - - smtp
-o smtp_send_xforward_command=yes
127.0.0.1:8026 inet n - n - - smtpd
-o content_filter=
-o receive_override_options=no_unknown_recipient_chec ks,no_header_body_checks
-o smtpd_helo_restrictions=
-o smtpd_client_restrictions=
-o smtpd_sender_restrictions=
-o smtpd_recipient_restrictions=permit_mynetworks,rej ect
-o mynetworks=127.0.0.0/8
-o smtpd_authorized_xforward_hosts=127.0.0.0/8

What i do:
1. Change master.cf.in
2. Disable standart antispam and antivirus from admin console
3. Add these strings to conf/zmmta.cf to section "SECTION mta":
POSTCONF content_filter LOCAL postfix_content_filter
POSTCONF receive_override_options LOCAL postfix_receive_override_options
than apply these settings by
zmlocalconfig -e postfix_content_filter=scan:127.0.0.1:8025 and
zmlocalconfig -e postfix_receive_override_options=no_address_mappin gs

These configs applies successfully and my zimbra worked with drweb antispam.

!!!BUT!!!
Several times a week, mostly at night, at different times
value of parameter content_filter from postfix/conf/main.cf becomes empty.
ie:
#cat /opt/zimbra/postfix/conf/main.cf | grep content
content_filter =
#
but must be:
#cat /opt/zimbra/postfix/conf/main.cf | grep content
content_filter = scan:127.0.0.1:8025

After that i reconfigure
zmlocalconfig -e postfix_content_filter=scan:127.0.0.1:8025
and restatrt mta
$zmmtactl restart
and antispam worked again.

Tell me, how to diagnose this problem?
Thank you!