Why does Roku drop Plex connection but not Youtube etc



this has started happening the last week or so. Roku plays Youtube, TED etc seamlessly but gotten to where I can't get more than a few seconds into video on Plex then Roku announces I've lost wifi connection and directs me to the network screen to reset. Currently I'm trying to play a 241 mb MKV file with separate SRT file (sometimes the subtitles show up, sometimes not). I've tried changing the WIFI channel to 11. Roku always says the internet connection is excellent or strong but this continues to happen. Also occasionally I get an onscreen Plex prompt about not being able to make a "direct connection." Should I wait for this to fix itself as happened with other problems or is it time to get Amazon firestick. BTW is plex free on Amazon like it is on Roku? thanks for any help!


p.s. I am using Roku stick powered by USB on the TV, I don't remember if it came with a wall outlet connection anyway I don't have one. Also I can't move the router any closer to the stick because the router has to stay in the kitchen according to the AT&T person who installed it.