Question about "writing metadata" errors

MacOS 13.6.1, MBP 2019, LrC 13.0.1

[ Despite all of what follows, the metadata error flags are popping back up again. So listen to JohanElzenga and just wait for the fix.] Suddenly many of my files are showing the "The metadata for this photo has been changed in Lightroom. Save the changes to disk?" Exclamation Mark. It also appears that all of the files I have editied show "There was an unknown error while writing metadata to this photo. Retry?" Down Arrow. At least in the latter case when I use Metadata search tool and click the "Editied" filter, all files have the Down Arrow. Both seem to resolve themselves fine when I click Retry or Save

Two changes I made recently may be related to this.

1. I moved the catalog from the external drive where my photos are stored to my local disk. (I have iCloud Drive but Desktop and Documents syncing is NOT enabled). The external drive gets backed up with Time Machine and a cloud backup. It has been this way for about 3 years.

2. Enabled full disk access to get rid of the LrC pop up complaining about lack of access standard folders.

Other change I have also made recently but I don't recall seeing the exclamation mark subsequently (but maybe I didn't notice)

- Upgrade from LrC 12.? to  13.0.1.

I see that I can select multiple and they will resolve but  any idea why this is suddenly an issue?  

For the Down Arrow, when I click Save, the condition goes away but it does update the file, extending the size of the file by about 4K and of course the modified date change to today.  I thought LrC doesn't update the files on disk, just the catalog?

For the Exclamation Mark, I could do "Import from Disk" so that the file backup is not forced but what might be lost?

This all seems rather odd.

Thank you,

Harry