Thanks for posting and glad you figured it out in the end.
What twigs for me is your statement here
said by telserv:that the pfSense firewall / router showing between 4 and 10% packet loss on the WAN connection.
a) how was pfsense configured to do this in the first place, and b) to what target(s) was it setup to do so?
If it was set up as a basic ping test done periodic from the PFSENSE to target w.x.y.z, and NORMAL conditions is
0% loss, then that'd IMMEDIATELY alert me to start looking at the pfsense itself and work my way upstream to your ISP.
said by telserv:that small amount of lost packets shouldn't cause a complete outage, shouldn't it??
Depends on a couple of factors. ICMP is the simplest way to verify end-to-end connectivity, but it shouldn't
be relied on exclusively to figure out whether something is or isn't working.
My 00000010bits
Regards