Why is my iPhone 4s Videos app displaying TV show episode and series titles as "Unknown" and Season as "(null)" and how do I fix it?
Have you already tried completely turning off TV show syncing in iTunes?
Also maybe give deleting all your videos from within the settings app at Genereal > Usage and here look for the Videos app.

As a last resort remains always a complete iOS Restore using iTunes or the option in the iPhones settings app under General > Reset > Reset All Settings/Erase All Content and Settings. Make sure to either have a backup in your iCloud or on your computer using iTunes.