@briang70
Yep, have same issue. I've solved this with disable MITM mode before, but today i tried clear cache and is helped.
Dec 4 05:00:10 kernel pid 85818 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:00:11 kernel pid 86437 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:00:13 kernel pid 96986 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:00:15 kernel pid 654 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:00:16 kernel pid 3896 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:00:18 kernel pid 7281 (squid), jid 0, uid 100: exited on signal 6
Dec 4 05:01:05 Squid_Alarm 81770 Squid has exited. Reconfiguring filter.
Dec 4 05:01:05 Squid_Alarm 82248 Attempting restart...
Dec 4 05:01:08 Squid_Alarm 90439 Reconfiguring filter...
Dec 4 05:01:08 check_reload_status Reloading filter
Dec 4 05:01:10 php-fpm 44241 /rc.filter_configure_sync: [squid] Installed but not started. Not installing 'nat' rules.
Dec 4 05:01:10 php-fpm 44241 /rc.filter_configure_sync: [squid] Installed but not started. Not installing 'pfearly' rules.
Dec 4 05:01:10 php-fpm 44241 /rc.filter_configure_sync: [squid] Installed but not started. Not installing 'filter' rules.
in this thread we talking about it, and waiting for resolving
https://forum.netgate.com/topic/153933/solved-squid-0-4-44_25-assertion-failed-http-cc-1533-comm-monitorsread-serverconnection-fd
In PfSense redmine is created task https://redmine.pfsense.org/issues/10608
Need to wait for new ported squid version for PfSense. In FreeBSD this issue already patched.