Recently took advantage of the 50% off deal on 2nd gen Fire Cube. I connected it to my HTC via HDMI and connected it to my secondary VPN router via ethernet. I turned on Developer options and side loaded Kodi with a few video add ons. However, could not get videos to play unless I punched them up to 2x FF. Also, no volume for the brief time they played at regular speed, before stopping. I decided to try playing some prime video trailers. They, too would not play.
I disconnected the 2nd Cube, replacing it with my original Cube, then set up 2nd gen Cube on WiFi without my VPN. Both Cubes worked flawlessly. Is the OS the culprit?