Strange glitches on a video after EVERY export and/or render

I’ve been battling an annoying Render/ Export glitch for the past 3 weeks on a video project for a client using live footage from a gig.

Every time I try to either export or render the video, I get these weird pixelated distortion glitches in the same places right through the 3min video. The glitches mostly appear when the stage lights pulse.

The weirdest thing is that the playback on my timeline is totally fine.. So much so, that I ended up screen recording the Playback so I could send a progress edit to the client.

Here's a video I've uploaded to show what the glitches look like: https://www.youtube.com/watch?v=2BHPBCtBoto

In the video, I’ve marked the Playback Screen Recording version (to show what it should look like) and then the render glitches.

So far I’ve tried all the things listed below, and no matter what, the glitches appear in the same place… I’ve tried:

1. Sending the export to media encoder (tried both GPU Acceleration and Software Only)
2. Rendering In to Out before exporting (glitches then appear on the render in the timeline)
3. Converting the source footage to different formats like MP4, MPEG, and MOV
4. Completely uninstalling Premiere Pro (removing preferences) and reinstalling
5. Saving the project (and source files) to an external hard drive and exporting it from another persons computer
6. Paying someone on Fiver to try export the project from their system.

I’m all out of ideas and it’s driving me completely crazy. Any help would be EXTREMELY APPRECIATED. I'm almost at the stage where buying Final Cut Pro and trying it on there is my only option...

My MacBook Specs

MacBook Pro (13-inch, M1, 2020)

Chip: Apple M1

Memory: 8GB

Cores: 8 (4 performance and 4 efficiency)