[2.4.4 FUYZ] Child prisoners appear in their liege's dungeon after converting to captor's culture

[KelrynGrey]

The prisoner in the image was sitting in my dungeon, being educated by my ruler just prior to this screenshot. I got the event to gain prestige from teaching him to act properly norse and he immediately disappeared and reappeared at home, still imprisoned.

 

[KelrynGrey]

Addendum - it looks like ANY event that affects the character has a chance to cause them to reappear in their homeland.
This character became brave and teleported home.

It is currently extremely difficult to successfully educate captives.

Edit: I started a new game, granted myself some captives, and now I can't seem to reproduce the problem. This is of course because in my main game I'm playing Ironman and we all know that bugs only like to pop up in Ironman.