Probably I found the solution here
The fix is indeed to disable Asterisk console mode (don’t use “-c” when running under docker, ever). I want to say this is an Asterisk bug, but even at 100% CPU use to keep up, Docker really should quash these duplicates somehow as well to avoid logging buffer explosion.
At least with the command
CMD /usr/sbin/asterisk -vvvvvvvvfp
there are no zeros in JSON logs anymore.