P: Save Metadata To File doesn't change metadata status, Read Metadata From File doesn't always work

@Simon Dalg, please do the menu command Help > System Info and copy/paste the first ten lines here.

I do not believe the update of 12/13/21 has corrected this issue.

I have been operating for many months without a problem and updated lighroom in April 2022. Based on a recommendation from Tim Grey I turned on "Automatically write changes to XMP"

Catalog Settings > Metadata > "Automatically write changes to XMP"

Immediately after this, while in Grid view multiples files started appearing with an ! in the top Right hand corner. The message was "There was an unknown error while writing metadata to this photo. Retry?" 

Two options appear

-  Import settings from disk (This appears to overwite all settings and remove keywords)

- Retry metada export ... this then says "Photos have read-only access" (which is incorrect)

Any assistance would be appreciated.

Why conversations get merged:

https://feedback.photoshop.com/conversations/lightroom-classic/lightroom-auto-import-to-folders-organized-by-date/5f5f44f14b561a3d422ab0ba?commentId=5f5f48984b561a3d422bdf45 

"If the crop is added by another application after the initial Import,"  It would be helpful for reproducing this issue if you could include an example application or two that causes this behavior. 

Starting with LR Classic v10.2, the Read Metadata from file option is no longer finding the crop info from the XMP metadata section. The same issue exists with the v10.3 update.  If the file has a crop during the initial Import, then the crop will be found and applied to the image.  If the crop is added by another application after the initial Import, then you used to be able to use the Read the Metadata from file option and the crop would then be applied to the image. Star ratings, color labels and keywords are all updated when using the Read Metadata from file option, but not the crop.  The only current work around is to remove the file from the catalog and then re-import the image. This problem is in both the Mac and Windows versions of Lightroom Classic.

I recently encountered this bug (save metadata to file not actually updating), and thankfully was able to get around it by enabling the "Automatically write change into XMP; once I enabled that LR seemed to update the XMP's correctly in the background.

Given this data point, I assume there is some difference in functionality internally between manually saving metadata vs the automatic feature.

By the way, regarding the read-metadata-from-file bug, I've used the following workarounds:

-- Most obviously, just restoring an earlier version of the Lr catalog from backup (although disconcertingly once I learned about this bug I've found a bunch of old photos that got corrupted because of it, too far back to recover).

-- When read-from-file damages metadata beyond develop settings, which it seems to have done to a bunch of my files (messing up capture time in particular): delete the xmp sidecar file and then read from file again, which seems to restore the metadata from the raw file successfully (so you lose any develop settings, but at least you get the camera metadata back). This might be reason alone to avoid DNGs until Adobe fixes the metadata read/write bugs.

I don't know what's different about your situation but nothing I've read from John's posts apply to mine and I haven't had any problems.  I've spent quite a bit of time comparing current files to backups.

That said, given that John says Read Metadata from File is unsafe I'll probably quit using it and hope that Adobe doesn't take years to fix the problem.  Not holding my breath.

WARNING -- DO NOT DO THIS!

As you'll see from John's explanation above, read from file has serious bugs. Contrary to expectation, save followed by read *can* change a file. I myself am still recovering from the incident I describe above (under a different username -- sorry, have separate work and personal accounts) and after spending many hours reconstructing from backups I still have many files corrupted and long develop histories lost.