Metadata from Photo Mechanic not importing into Lightroom when working from external SSD

​@JohanElzenga Do the XMP files have an .xmp extension or .XMP extension (so lower or upper caps)? I vaguely remember that there was a problem in the past with upper caps from Photo Mechanic not being recognized. If you can change this in PM, then try that.

Right. Photo Mechanic by default writes the extension in upper case (.XMP), while LR looks for lower case (.xmp). On case-insensitive volumes (the default for Mac OS), there’s no issue. But for case-sensitive volumes, LR won’t find the .XMP sidecars created by Photo Mechanic.  Two solutions:

1. Change the volume to be case-insensitive.

2. In Photo Mechanic, set the option Preferences > Files > File Extensions to use Lower Case Extensions. That was valid at least as of 3 years ago: 

When you import, are you applying a metadata template that might overwrite the PM values? Open Import, and review the Apply During Import section. Is a template specified? If so, open it and see which fields are checked.

Good evening everyone, and thank you for your replies. 

For your information, in the afternoon I carried out several workflow tests under different scenarios. I tried keeping the catalog on Mac with the photos stored on the external SSD and also the opposite configuration, with the catalog on the SSD and the photos on Mac. In all cases, the issue occurred consistently and exclusively when the folder from which Lightroom was importing the photos was located on the SSD.

I did not change any settings in either Photo Mechanic or Lightroom during these tests. In fact, as I mentioned before, I had not touched any preferences at all: in the morning my usual workflow was working correctly, while in the afternoon the exact same workflow, when moved entirely to the SSD, resulted in metadata being lost.

This led me to conclusion that the problem might be related to how Lightroom was reading the photos stored on the SSD. Probably due to the file system, which may have some access restrictions or block-level behaviors. As a result, I tried to reinitialize the SSD, switching the file system from APFS to ExFAT, and this resolved the issue.

There is probably a way to bypass this incorrect file reading while keeping the file system in APFS, but I am not aware of how to do so.

I can’t imagine how the disk itself could cause this. If I were you, I would check the .xmp files (if RAW) or the actual photo files (if not RAW) after you tag them in PhotoMechanic and before you import them into LrC to see if the metadata is actually in there.

“Nothing else in my workflow has changed”

Yes, we hear that a lot, and many times it turns out that something has changed without the user realizing it. I think this is the place you need to check and double check and triple check.

Did you verify that PhotoMechanic has written the metadata to XMP files that are in the same folder as the originals?