I have the same issues but worse, none of the recorded video's will play from the web (on any browser) or from the Channels DRV add on a Fire Stick or Fire TV. Video starts and spins but just stops.
If I go to the library where all the videos are stores I can play them from a pc or using a separate video player on the Fire TV.
So the Recordings are good, its something to do with the DVR playback.
Using a Synology, have tried reinstalling, even did a clean reinstall and then imported the video's, but even new shows being recorded will not play back.