I've posted a few times in the past about my setup suffering from random kernel panics.
In an effort to try and troubleshoot I temporarily switched my main firewall/router to t1n1wall and discovered that the SNMP process has a memory leak.
root 103 0.0 60.7 1252832 1250388 - S 6Jun19 19:48.53 /usr/local/sbin/snmpd -c /var/etc/snmpd.conf -p /var/run/snmpd.pid
I have yet to test it, but my theory is that it's possible that the same thing is happening in OPNsense.
A memory leak of a user space process cannot be an issue. It may never raise a kernel panic.