Export window taking forever to open, and eventually won't open at all

I have a big project that has developed a crazy annoying issue. When I want to export, the export window comes up more slowly than usual. Then if I want to export again, it comes up even slower. Eventually, it stops coming up at all. 

I have tried:

- Downgrading to Premiere Pro 24.6.0.

- trashed preferences

- uninstalled all third party plug ins

- imported the project into a fresh project

- dumped/rebuilt all my pek files.

- removed a couple of high resolution photos I thought may be the problem.

Still no fix. 

My system is a Mac Studio running OS Sequoia 15.0.1.