I've been seeing strange behavior with my OpnSense router. Occasionally, my gaming PC (on VLAN 10) got kicked out of online game server, active SSH session from VLAN 20 to a local server on VLAN 30 is dropped with 'broken pipe' error. These events always occur at same time. It's almost like i go to Firewall > Diagnostics > States Reset on Web GUI and click big Reset button.
Frequency of this problem varies from zero in 10+ hours to several occurrences within hour at evening.
How do I narrow down the cause of this strange issue? Could hardware (bad cables, bad NIC, ....) be the reason that triggered the reset of firewall states?
Maybe your gateway disconnects and reconnects briefly? There's a setting in the advanced firewall tab, something like "Disable state killing on gateway failure" or so.