Editing Smart Object in Camera Raw. Not all masks showing.

Sonoma 14.3.1 / PS 25.4 / Camera Raw 16.1.1 on Mac Ultra M1 128GB

Editing for the past 2 hours of an Smart Object which requires fine masking. Going in and out of SO / Camera Raw to review edits. I save the xmp file before I close ACR. The first xmp fille is 219k and the last is 3.7MB. The psb file is 1.23GB. Too big to attach. The xmp file is attached however.

Looking at the 3.7MB file using textedit I can see the XML for the mask called "tree", however ACR is not showing it in the last iteration. 2 hours of editing lost.

I have had an issue before with a lost mask when the xmp file gets this large. Not fun.