Hi,
This is a known issue across all platforms with Thralls rescued using the Jailor’s Key. They have resolved the issue in testlive 2.7, so the update will probably be live in a few weeks.
Most instances of this were fixed several patches ago, but if you are aware of any Thralls that still exhibit that behaviour you should make a seperate bug report.
This has also been resolved in testlive. 
Good luck