Whilst I was on holiday, I went through some images on my laptop, adding captions (no tags) to them and deleting some. I now want to transfer the images back to my main desktop PC, taking the new captions with me. The two machines do not share a database, both use the default sqlite database. Images are from-camera JPEGs.

Album 1:
1. I verified on the laptop (source machine) that captions had been written to all the configured fields in the file (default list including Xmp.tiff.ImageDescription and Xmp.dc.description).
2. I then copied the image files using scp to the desktop PC
3. I started Digikam and let it scan for new items (set to happen at startup)
4. I went to the newly copied album, and did "Album > Reread metadata from images". In the past I have used this to read in the captions from the file data.
5. It didn't work, and neither did the same entry on the Item menu. The "completed" message popped up so quickly and with no disk activity that I don't think it actually checked the images at all. Certainly much quicker than generating a thumbnail.
6.Opening the metadata editor window at this point showed all the fields filled in with the caption, but even after clicking OK, the image thumbnail and captions tab of the right-hand side bar had no caption available.
7. After much cursing, I tried selecting one image, and using the "More > Read metadata from file to Database" button in the captions tab of the right-hand side bar. This worked, read the file and populated the thumbnail / sidebar. Manually working through each file in the album got the information into the database.
So this has a work-around, but a painful one for any number of images.

Album 2:
I went to repeat this, but found the other two albums have not had the captions written to the files on the source machine. So I am stuck even earlier:
- No amount of Album > Write Metadata to Images writes it out
- Again the completed notification is instant, far faster than disk access times on this machine.
- More > Write Metadata to each file button in the right-hand side bar is greyed out
- I have tried turning lazy synchronisation off, no change.
- I tried altering the preferences so that an XMP sidecar is written as well as to the image file, but no sidecar files are written!
- If I edit the caption again and then click Apply the changed caption is written out, but this means manually altering (no-op) every single caption by hand (as they are different to each other).
A potential work-around exists but is very labour intensive.

I think I am correct to say that when I completed editing captions on this album (with lazy sync turned on) I just quit Digikam, without manually telling it to sync changes, where as I synced changes by hand on Album 1. Does this mean that sync-pending-changes-on-exit is broken as well?

I am in the process of updating to Digikam 5.6.0 to see if anything changes.