Connections drop on settings change

[theshao]

I have several pfSense firewalls but one is behaving somewhat differently to the others.
The one I installed most recently seems to drop all active connections whenever I apply almost any setting (firewall rules, static routes, changes to interfaces that aren't even enabled), with the only entries in the system log being:

Aug  5 15:17:26 pfSense check_reload_status: Syncing firewall
Aug  5 15:17:34 pfSense check_reload_status: Reloading filter

Is this expected behaviour? It comes back up after a minute or so and carries on perfectly happily but my other firewalls don't drop active connections under these circumstances.

[theshao]

Some further observations on this.
I have several static route, under Advanced --> Routing.
If I click the "delete" icon next to the route, then "OK" the prompt, the rule is deleted immediately, without any "apply" button, and without dropping active connections.?
If, on the other hand, I click the "disable" button, then "Apply", connections drop as described above. Anyone got any ideas why this might happen?