Digikam 8.4.0 is missing Tags

I noticed that some of my old (2018) photos were now appearing in the No Tags list, so I selected them and reread metadata. The JPEG and associated XMP both show the correct tags, but digikam refuses to read them.
I’ve tried changing digikam settings to read the data from the picture, not xmp, but that makes no difference.
Is this a bug introduced in 8.4.0, or something else?
Thanks in advance
Steve