P: "Save Metadata to File" overwrites EXIF tag SubSecTimeOriginal

Here's a test library:

https://www.icloud.com/iclouddrive/0b3ffGjOxRmVDHtdo6YhcvalA#subsecond-test

I did notice some intermittency while testing. But it seems I can pretty reliably reproduce by:

1) Download & unzip the library

2) Inspect the files

$ -> cd ~/Downloads/subsecond-test/Photos/Import/Test/

$ -> exiftool -G -s -SubSecTimeOriginal IMG_6067.HEIC IMG_6097.HEIC IMG_6175.HEIC 

======== IMG_6067.HEIC

[EXIF]          SubSecTimeOriginal              : 389

======== IMG_6097.HEIC

[EXIF]          SubSecTimeOriginal              : 747

======== IMG_6175.HEIC

[EXIF]          SubSecTimeOriginal              : 366

    3 image files read

3) Open the library, select all 3 files, edit metadata (I remove the "Review Place" keyword), do "Save Metadata to Files"

4) Inspect the files again

$ -> exiftool -G -s -SubSecTimeOriginal IMG_6067.HEIC IMG_6097.HEIC IMG_6175.HEIC 

======== IMG_6067.HEIC

Warning: [minor] Bad format (16) for MakerNotes entry 14 - IMG_6067.HEIC

======== IMG_6097.HEIC

Warning: [minor] Bad format (16) for MakerNotes entry 13 - IMG_6097.HEIC

======== IMG_6175.HEIC

[EXIF]          SubSecTimeOriginal              : 366

    3 image files read

Hmm, following your steps, I don't see the misbehavior -- EXIF:SubjectTimeOriginal is preserved, with Iphone HEICs, JPEGs, and .xmp sidecars of .CR3s.

In these cases, I've found the most reliable way of demonstrating a bug is by sharing a small test catalog including the photo(s) illustrating the problem.

1. Select one or more problem photos that haven't yet been polluted by Save Metadata To File.

2. Do the menu command File > Export As Catalog with just the option Export Negative Files checked.

3. Zip up the exported catalog folder and upload it to Dropbox, Google Drive, or similar, and post the sharing link here.

Adobe generally won't pay attention unless they can easily reproduce the problem.

Clarification on (3): I don't believe the command does anything until you change some metadata first. I think I flagged or unflagged the file as part of this step.