I also have had the same experience where the Tablo app on X-Box One S just randomly quits. Either I'm watching live TV or Recordings.
I also have troubles fast forwarding on the Tablo App via X-Box One S from any recordings. Every time I try to fast forward (joystick to the right showing progress bar) to any section of the recording, it goes right back to the beginning of the recording. I then tried the "RT" button on the Xbox and that works but only fast forwards to like every 20seconds but the problem is if I click on the "RT" button quickly to many times (to fast forward to 2minutes), the recordings goes right back to the beginning. Basically, the fast forwarding capability is virtually impossible to use on the X-Box One S - Table App.
The iPhone and iPad fast forwarding capability works like a champ. Also using Chromecast via Chrome browser - fast forwarding also works with no problems. That leads me to say that the X-Box one S app has many bugs in it which is unfortunate because the console is my main entertainment center.