Rendering a particular project no longer allows a fast export

Hi all 😊

I have a strange problem that's only affecting one project ... it's not long (3 minutes) but it has lots of overlapping plugins which track multiple areas of land (the project contains aerial footage) and also add hovering markers over the footage.

Firstly, it's INCREDIBLY slow to render, probably in the region of 1.5 hours on a top of the range M1 Max MacBook Pro with 64GB of RAM ... normally a file of this length will take a few minutes to render tops!

But then frustratingly, normally once you've rendered a project, the actual export will be much quicker ... but in this project it takes as long to export the rendered project as it does to render it in the first place!

I've tried copying the contents of the project into a new project (which sometimes clears random bugs like this), but it makes no difference ...

Is there anything I can try to fix this issue where exporting the rendered project takes forever?

Oh also, once the project is rendered, if I then quit and re-open FCPX the rendering has gone (the dotted grey bar appears above the footage in the timeline) so I have to render it again! It's as if it's rendering the project but not permanently saving the render files – you can play back the rendered project no problem, so long as you don't quit and re-open the program ...

Many thanks for any suggestions you can offer of how to fix this!

David

PS. I'm running FCPX 10.6.3 on Monterey 12.3.1.