Two AppleTV app issues remain:
When watching a new recording, playback will return back to the beginning of the recording after about 15 to 30 seconds.
When watching a new recording, and skipping past commercials around midway of the show, the playhead will jump to the end of the show.
Both issues are 100% reproducible, and have been broken for a LONG time now. I’m even seeing these problems using the Tablo iOS apps.
Very frustrating.
I haven’t had the second issue you mentioned, on my Apple TV 4K (1st gen). But I do consistently have the first issue where it’ll jump back to the start of the recording after 15ish seconds. I know this has been brought up before, Hopefully a fix is on the way eventually.
I have had occurrences of both problems now and then. I usually just play with it a while to work around it. It isn’t catastrophic though. Sometimes I just start at the beginning and FF to the time I left off at.
But here is another problem I’m having. Again, it’s not a disaster; and I play with it until I get the correct function. Keep in mind I’m 77, hard of hearing and have tinnitus. The Closed Captioning doesn’t always work properly. The program does need tweaking with some recorded programs. But this CC problem only affects those of us who have poor hearing and need the CC.
It is nice to have devices that work from Wifi using an outside antenna. I have one 2 tuner Tablo and now another Tablo with 4 tuners, both working through the Apple TVs. It would be nice to have all 6 functioning perfectly. I may not have too much time left at 77. 
By the way both my Tablos are 4th Gen.