We have a RCA 32" Roku in one bedroom, and a 43" Hisense Roku in another. Both TV's played both Prime and Plex with NO issues until recently. Our 55" LG, 2 **bleep** laptops, and 2 decent Desktops "ALL" play Plex and Prime without any issues. The LG and the 2 desktops are cat6 hardwired to the router, and the laptops are wireless. I even tried Plex and Prime on our phones with no issues. Our internet is a 1GB. fiber optic that runs consistently above 800gb per.sec.
Both Roku TV's sit within 25 ft of our Netgear Nighthawk Dual 2300 router, and both show 4 bars regarding the wireless connection every single time. Have tried the wireless connection on both 2.4G and 5G, with the same issue. Other than our phones, there is never more than two devices running on the internet at any given time. Yet every single time both Plex and Prime will play for 1-2 minutes and then kick out..At times when they kick out we get a message to check connection. We do and it shows we're connected. This problem we have had on occasion, but has been constant since the last update. And surprise, surprise, we also are on the free program!(could it be just a coincidence??.) For the record it matters not the time of day be it 9am., 6pm., or 3am. the issue persists.
I paid for lifetime Plex, I pay for Prime, and I get over 65 channels with our aerial. We really do not need more. By paying for the TV's, we have also paid for Roku which is the operating system. Some examples: Phones running android, computers running Windows, etc.
I have Cold Booted Every piece of electronic gear in our home. Reconfigured the router, checked all updates (installed any I found) and still since Roku's last update nothing solves the issue. Evidence all seems to point to an issue in the programming code for the wireless connections. I believe the only two options left is to contact the TV manufacturers plus both Plex and Prime. If no one can help, then last option is ask for a refund from the manufacturers, then replace both TV's with brands that will play what we want.