strange behaviour of dovecot

Dear dovecot-list,

Dovecot gives the below error messages and those errors go away after running 'systemctl restart dovecot'(Restarting dovecot service)', however, the same happens after a while later(like after 300 mails delivered).

master : Error : service(anvil) : Initial Status notification no received in 30 seconds, killing the process master : Error : service(log) : Initial Status notification no received in 30 seconds, killing the process master : Error : service(ssl-params) : Initial Status notification no received in 30 seconds, killing the process master : Error : service(log) : child 3703 killed with signal 9

then the log process is not there so that no mail log gets captured in maillog:

root 28036 0.0 0.0 19864 1604 ? Ss 11:45 0:00 /usr/sbin/dovecot -F dovecot 28074 0.0 0.0 9312 1000 ? S 11:46 0:00 dovecot/anvil root 28075 0.0 0.0 12324 2084 ? S 11:46 0:00 dovecot/config

Does this have something to do with any limitation in dovecot configuration?

If anyone in the list ever has similar or same experience, please give me a clue that shows where to look at from here.

Thanks,

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Masaharu Kawada