Amazon FireTV – Random Pixelation

I have multiple AFTVs in my house that are hardwired to a NAS that stores my MKV files. When I play those files through Kodi, I encounter random pixelated screens during playback. If I play those same files with VLC on the AFTV, the files play fine. Is there a setting that I need to adjust? I have an old Kodibuntu machine that also plays the files fine, so there must be some setting on the AFTV, but I can’t find it.

I mainly see this problem with animated movies and shows, but also see it with live action as well.

Thanks in advance!