Bad playback for a rented movie

Request a refund for an App Store or iTunes Store

https://support.apple.com/en-ca/HT204084

Playback quality is dependent on the network connection so best to verify that. You are free to request a refund but it would be up to their discretion and if there is an underlying issue then it could occur again.

Check speedtest to see current internet connection

Make sure DNS is set to auto

If on wifi try ethernet

To see a current status of the network get a report using istumbler, netstumbler or similar. Look for signal strength, noise, nearby networks

And If you can't watch or stream movies and TV shows in the Apple TV app - Apple Support