How many hard drives are you using?
Get rid of the external drive for Premiere and use internals.
Set up scratch files and internal drives properly.
As far as drives go, I don't usually use external drives. But seeing that an external USB3 drive worked perfectly with my friends Laptop shows thats not the issue. I've also tried the footage on my internal SSD and Raid. No difference for me.
How do you recommend setting up scratch disks? I've tried a few things and none of them have made a difference.
Start with some of the tips in the hardware forum.
Why do scratch disks matter when i'm not rendering any effects? Regardless, I've tried the scratch disk on every drive... and no difference in results. I don't think its the scratch disk locations.