4K render too slow! Premiere render taking 4 hours - usually much faster

Hi all! I'm on a Mac Studio with an M1 Ultra chip, 128GB of RAM and an 8TB drive. I'm trying to render a 3 minute long video that uses multiple Adobe stock files and some linked AE comps that contain basic animations with minimal FX, using the attached settings.

I've rendered many similarly-sized files with the same settings and they've never taken 4 hours, and I'm not sure what could be causing this. One time I rendered, after 4 hours it said it was done and gave me a green checkmark, but I only had a zero byte mp4 file and an xml file as a result. It either takes 4+ hours to do but looks great, or doesn't render.

The attached settings are what I always use for a high quality 4K render and my render times are normally MUCH faster than this. I've tried creating a new sequence in the same Premiere file and copied/pasted the contents in before exporting, same result. I've also been cleaning out my media cache before every render. I even tried plopping the contents into a brand new Premiere file--no luck. Anything else I can try??