Same exact issue here. I just upgraded to Frontier Fios around Sep 2022 and I purchased this Roku shortly thereafter. I imagine the modem I was provided through Froniter is new enough and I've checked around the eeos settings for a fix, to no avail... I have also tried all other recommended steps, restarting my home network, resetting network on Roku, disconnecting then reconnecting the WiFi on Roku, restarting the Roku. Nothing works except for the factory reset!
One interesting finding: the first time a wifi disruption happened, I found that I could connect to my mobile hotspot easily enough and use Roku through that network instead of my home network. I did ultimately do a hard reset on Roku and successfully connect my home network, though, and it worked well for a few weeks. However, the next time a wifi disruption happened, the mobile hotspot backup didn't even work, so I had to do the hard reset again on my Roku before I could connect it to any network.
I know plenty of people using these devices without issue, and I really don't understand the prob... maybe I am coincidentally missing some critical Roku system update for the few hrs I leave it disconnected from wifi when a disruption happens? and then by the time I manually reconnect the Roku to my home network, Roku can't function properly using the network due to the system update that it missed? Lololol... in any case, for me, it is not really worth the hassle to go through the factory reset when I have a wifi disruption, esp having frequent guests who use the Roku connected TV. I'll prob switch back to Chromecast/Firestick if those will work better with my wifi situation unless there's a better solution that doesn't involve the replacement or enhancement of my home internet services/equipment.
