Balance One loosing internet connectivity seemingly random, cannot recover

This would be consistent with my experiences, in which I find that a VLAN with an Outbound Priority set, will sometimes stop working for no reason. A quick test is to revert to firmware 8.4.1 and see if your problems go away.

If so, you can add yet another person to the long list of us having serious troubles with firmware 8.5.0 and 8.5.1.

See Outbound Policy + Firewall + VLAN bug in firmware 8.5 - #20 by soylentgreen