I experience similar problems on my 49UF680V.
The app started acting up around three months ago, often skipping ads during playback (which I wasn't mad at) and shortly after it started to hang either after ad playback or directly when starting video playback. Since around a week ago, I can view circa two videos until the app hangs during ad playback. After a short time, the TV shows an "Out of memory" notification and automatically reboots.
I just ordered an used chromecast for cheap until these issues are resolved