Thumbnails for video files not generating

Hello! I've recently begun using Bridge, and thumbnails are not generating for (most) of my video clips. They do generate for photos and other graphics (ai. etc). Screenshot attached from my user->movies folder where only one thumbnail is generated. There's nothing fundamentally different about that particular file as far as I know. It's 35mb and there are other mp4s that are smaller and larger. Most other folders elsewhere on the computer don't generate thumbnails either. The desktop shows them, but if I move more mp4s onto the desktop, they don't generate.

Steps taken so far to troubleshoot:

• Purged Caches in Bridge
• Reset Preferences on Bridge, Premiere.
• Reinstalled Bridge and Camera Raw
• Moved location of Bridge media cache 
• Increased thumbnail cache limit (many of the video files are well below 1000mb anyway)
• Refreshed folders (F5)

Specs:

2017 iMac 3.8ghz quadcore i5, 24gb RAM. 8gb radeon, OS 11.6

Bridge v12 (also didn't work on previous version)

I'm at a loss, any suggestions are appreciated!