XMP Saving Issue Preventing Opening Photos

I have been using Lightroom professionally for 10 years, and yesterday started having an issue that I have never had before, and it has seemingly completely prevented me from opening photos in Photoshop through Lightroom.

(1) When I tried to open a Lightroom image in an externam editor (Photoshop 2025), I would first have to wait about an hour or more for the XMP to be written for all 200,000+ photos in my catalog. Then the image would open. If I tried to open another photo after that, the entire XMP writing process would start all over again. (See attached screenshot)

(2) I went into Lightroom Catalog Settings and unchecked the "Automatically write changes into XMP". Then when I tried to open a photo in the external editor, I get a generic "Saving Metadata" message that just hangs and never completes. The image never opens in Photoshop. If I cancel the Saving Metadata process, the image also does not open in Photoshop.

(3) Remedial action taken:

-- I have deleted and rebuilt the Helper.

-- I have tried opening the catalog on a different computer.

-- I have tried opening a cloned/copied Lightroom catalog on a different drive 

-- I have tried opening in Photoshop 2024 and Photoshop Beta.

Nothing has allowed me to open an image in Lightroom Classic in an external editor.

(4) Anyone have some ideas for fixes? I don't know what my next step should be. Try to open a backup catalog? Try to rebuild the catalog in some way? Any help would be appreciated.

Some relevant Specs:

Mac OS Sequoia 15.5

Lightroom Classic 14.4