Firewalla Gold Frustrating Intermittent Connection Loss

Howdy,

One of my two Firewalla Golds has been acting strangely since I purchased it two months ago. LAN clients occasionally lose connection to the WAN/internet. Typically, Chrome displays the error "DNS_PROBE_FINISHED_NO_INTERNET". I've had a support case open for weeks, however Firewalla support has been useless. 

Topography and Symptoms:

Frontier Fiber ONT - Firewalla Gold in Router Mode - 24 port switch - wired computers and APs

Pings and traces to the WAN from wired PCs behind Gold occasionally fail, however most of the issues seem to impact wireless clients. Pings and communications to/from wireless clients fail about 40% of the time. I've replaced all APs, the 24-port switch, tested all cables, and had the ISP replace their ONT and test the incoming WAN cable. I'm not using any sort of private DNS or VPN on LAN devices. This issue doesn't impact my other Firewalla Gold (different network entirely). Also, when I replace the problematic Firewalla Gold with the ISP's router, the problem completely disappears. 

Firewalla insists that there is nothing wrong with this Firewalla Gold, however troubleshooting steps clearly point to the Firewalla Gold being defective here. Has anyone experienced a problem like this with their Firewalla? Do you have any additional troubleshooting recommendations? I suspect some kind of hardware fault with this Firewalla Gold.

Thanks in advance for your help!