I have a Roku3 4200X in my living room. It works well other than when using the "My Media" channel, used to stream videos located on my PC (using PlayOn as a media player). I have other Rokus in the house, and those keep working fine.
Issue is that I reach the video as usual, start playing it, it starts, and usually after 5 to 30 secs it stops playing all together.
I've tried to reset to factory settings... Re-installed everything. Same issues came back.