I edited several images in LR Classic. I moved the edited images to another folder; all at the same time. In the new folder there were 4 consecutive thumbnails that said the file was missing. I checked the new folder. The raw file and the xmp files were in the new folder.
I made the mistake of saying synchronize folder instead of saying find the missing files. The 4 files were uploaded but the XMP file information is not being applied to the RAW file. The XMP files are present in the new folder. I've checked them in a text editor and the information is intact.
When I did that the files showed the edited image ONLY when the file was selected and in the Develop mode.
If I went to another file or to the Libray mode the files did not show the edits even when selected.
I noticed that I could sync the settings to another file and the edit would stay and be seen in any mode.
So I made copies of just the RAW files in another folder. Selected both sets of images. Synced the unstable image with the new RAW image and the edits stuck. I deleted the original RAW files and moved the new ones to the folder with the rest of the images,
All I can say is that it was weird but I'm happy with the results.