understanding XML, Relinking files and new transcoding

Hi

Running FCPX 10.4.8 on catalina 10.15.5

Project settings of 1280x720 29.97 fps

using media that was captured from HDV tape that was 1440x1080 29.97i combined with footage shot on iphone 11 at 1280x720 30p

Fully edited with proxy media

once selected optimized, FCPX became sluggish, wouldn’t render, wouldn’t share, thumbnails slow to load, had to force quit if i wanted to close application, etc Every attempt to share project to file (using any codec) failed or crashed app.

Tried everything - created new library, new project, imported into new event/library/project. same issue

tried new user account. Failed with a video render error.

So here is where I am at. I exported XML.

I created new library. I took original files and transcoded everything externally using h264 so both sources start this way. I imported into brand new library. I “hid” my original files in another location. I imported XML and the newly created original media. On import, it is now transcoding all the original media into optimized and proxy media. I can see the XML I imported is showing “missing file”.

I want to make sure I’m even understanding my new attempt to work around my problem.

Once the newly imported media files are finished processing, will I be able to link my XML timeline to the new media? I did not change the file names when I transcoded with h264 externally.

I am just trying anything at this point but I want to make sure I understand what I’m actually trying to accomplish so I don’t mess it up. I haven’t ever used an XML with any other file than the original ones the XML was created with.

Thanks in advance