dovecot - May 2017 - dovecot: auth-worker: Fatal: master: service(auth-worker): child XXXXX killed with signal 11

Trying to track down a dovecot issue .... 

The error message is: 

dovecot: auth-worker: Fatal: master: service(auth-worker): child XXXXX
killed with signal 11 (core not dumped - set service auth-worker {
drop_priv_before_exec=yes }) 

The setup is dovecot 2.2.29.1 with passwd and mysql auth db's and a very
basic config. 

both authentications work ... the symptom is that after a connection is
made the auth worker loads and emails are downloaded and everything "is
fine". However, about 30 second to a minute after the connection is done
the process dies with the error message. Then the process starts all
over with on the next checking of email ,but again everything "works"
just seeing this error and the process dieing each time? 

enabled all extra verbose logging ,but nothing gives any clues.... 

Tried to enable core dumps ,but couldnt get core dumps to work ? 

The only thing is that a recently pkgsrc (netbsd) update create 2
packages, one for dovecot and one for mysql plugin , sense then now this
error appears. 

,but it appears the .so lib files are installed and linked correctly. 

Double checked all file permissions and user permissions as well as
chroot , etc, etc, ,etc.... 

cant seem to narrow this one down .... 

any ideas on trouble shooting would be great .... 

even tried running a trace with gdb -p on the process ,but it just dies
with a signal 11 ....