SUMMARY
Digikam seems to be duplicating EXIF tags when saving tags, i.e. the EXIF tags increase by 1 on every save.

First and foremost: I have to say I'm very new to Digikam (and image tagging in general), so not sure if I'm doing something wrong or not. But I've looked at it for a long time and I have no idea. Seems like some kind of bug to me, or at least unwanted behavior.

STEPS TO REPRODUCE
1. Open an image in Digikam. In my case a .jpg image. It has a few existing EXIF tags like Make, Model and Software.
2. Open Tools -> Edit Metadata and edit or add something. In my case I edit the Creation Date.
3. Click Apply and/or OK.
4. In Digikam everything looks great.
5. I open the image in ExifToolGUI and check out the EXIF tags: (nearly) all EXIF tags are now duplicate: there's 2x Make, 2x Model, 2x Software, 2x XResolution, 2x YResolution etc. etc.
6. If I edit something in Digikam again and save the file, and re-open in ExifToolGUI the tags are now 3x. Edit and re-open: 4x. Etc. The EXIF tags keep duplicating. Not that it is not an ExifToolGUI bug; I quickly checked in a hex viewer and indeed all tags appear multiple times.

OBSERVED RESULT
Duplicated tags.

EXPECTED RESULT
There are a couple things that are unexpected to me:
- First and foremost I (obviously) expect Digikam to not duplicate EXIF tags into infinity.
- Secondly, I kinda expect Digikam to (somehow) notify me about tags being duplicated in the file. In Digikam there's absolutely no indication or mention that the EXIF tags all appear n number of times. While it's nice that the UI doesn't get bloated with duplicated tags, some indication would be useful.
- Thirdly; if this does end up being a user-error instead of a bug (maybe I have to change a setting or something?): I still think it's kind of weird behavior and there should be some kind of warning or notification or something. Since Digikam itself doesn't show anything (that I could find at least) about duplicate tags (my point above); I would've never have noticed if I didn't open the file in ExifToolGUI.


SOFTWARE/OS VERSIONS
Windows: Windows 10 Pro