Fast forward skips back to beginning of show/movie

If I press the pad to pause a film then swipe to fast forward, the time stamp flickers between the time in the film and 0.00 (ie the start of the film) and no matter where I try and resume from it starts from the beginning. Several films & apps do this, including Apple TV native app. Tried restarting the Apple TV 4K box. Software is up to date. Have reset the connection to the Siri Remote. Only option is unplug the Apple TV 4K & plug back in to restart everything. Any ideas/help? It’s only about 3 months old.