Hello ,
Thanks for using the Apple Support Communities!
I understand from your post that movies you own are giving you a hard time during playback. Because you are experiencing multiple issues with movies you own, audio sync and buffering problems, the first troubleshooting steps I would recommend would be to further isolate.
You mentioned one specific movie, Fellowship of the Ring. Does this happen with other owned movies as well? Are these movies on your computer’s hard drive or are they located on an external hard drive?
If you can isolate the issue to a specific movie, I would suggest deleting that movie from your iTunes library and then download it again from your iTunes purchases as described in the following article.
Download your past purchases - Apple Support
If your movies are located on an external hard drive and you experience this issue with all movies, I would suggest moving a movie or two from the external hard drive to the computer’s iTunes library and then test.
The iTunes library location can be found in the following article.
Make sure that you're in Finder. From the menu bar at the top of your computer screen, choose Go > Home > Music > iTunes > Movies.
Locate and organize your iTunes media files - Apple Support
Once you move the movie to to the correct location on your Mac, you will need to import this movie into iTunes. To do this please follow the instructions from the next article.
In iTunes, choose File > Add to Library, locate a file or folder, and click Open.
Import music and video from a computer into iTunes
Cheers!
