Recoding .mp4 files efficiently to be playable on my TV? (HandBrake is slow)

Hey!

So I have a hard drive with videos that I usually hook up to my TV to watch, it normally works just fine. But for some reason, some of the .mp4 files cannot be played. It works just fine on the computer, but my TV says "File is invalid".

I found out that it probably has to do with the codec. So I tried to convert a file via HandBrake, and voilà, it worked! Looking at the files that can be played and ones that can't, I don't really see the difference when looking at the properties of the files (I'm no expert).

I checked "Webb Optimized" and "Passthru Common Metadata", and set the audio samplerate to 44.1, otherwise I made no changes to whatever HandBrake does.

So I do have a solution, however it took 15 minutes for the process, and I have 24 videos to recode. I was hoping someone knew more specifically what the issue is with these files, and if there's a quicker way to convert them?

Cheers