[digiKam-users] Face recognition results not cleaning up

[Sky Diver]

Hi,

Tech info:
----------
OS:         Ubuntu 18.04
Digikam: 5.6.0
DB type: Sqlite

The problem:
------------
I tried to have another go at the face recognition feature and I find
myself dealing with it for 3 days in a row now.
In an effort to get better results from the engine I tried to "Scan
the collection for faces" several times.
I tries to every option on the menu several times (skip scanned images
/ scan and merge / clean unconfirmed and rescan).
I also hit the "Clear and rebuild all training data" at least twice
(if not more).

A few times the application crashed with a nice message, many other
times the application would just close and disappear without warning.

The current situation is that when I have "Show Face Tags" switched
on, I see a lot of "ghost face-recognition frames" on many photos.
This means that I click the "remove" button and then there are no more
frames on the photo.
If I would then go to a different photo and come back to the first
one, these "ghost frame" would reappear there.

After failing to clean the Unknown + Unconfirmed results via the
various "scan collections for faces" options,
I realized I could just "select all" faces in both categories and
click the remove (red minus) button on one of them to have them all
being removed.

Sadly, even after doing that, I still have these "ghost frames" stuck
on many photos.

The problem with it is that when going into a photo in order to tag
faces, there are many duplicated frames with a slight offset between
them,
so the end result is that for a group photo with several faces on it,
there could be around 2-3 frames surrounding each face.
One frame might be the person's confirmed tag, but it would be covered
by another 1-2 frames with the full "Who is this person?" title along
with the "+"/"-" controls.

Clearly, something is not cleaning up correctly in the DB.
Taking a quick look at some tables I see that:
  UniqueHashes has ~33K rows
  FilePaths has ~35K rows
  CustomIdentifiers has 48K rows
  Thumbnails has ~82K rows

Questions:
----------
1. Can this be fixed by means of switching some option on/off in
digikam? (alternatively, is this addressed in a later version?)
2. In case digikam can't fix it, what would be the proper way to
remove all unknown+unconfirmed face frames via SQL?

Thank you.