Imapd dies

Hello,

I had dbmail working from years.

I encounter several imapd dies per day since a week.

The error message is "dbmail-imapd: dm_string.c:160: p_string_erase: 
Assertion `pos + len <= S->used' failed.".

The only recent change I can correlate may be the increase of dovecot 
number of process_min_avail.

Can it be related ?

Is there some guidance to define dovecot proxy settings specific to dbmail ?

Thank you