Encryption does not work on Fairphone 2

Summary

The encyrption process is not executed, after following the steps to encyrpt, device reboots and encyrption is not activated

Steps to reproduce

Click Security->Encryption->Encrypt Smartphone->Confirm->Enter PIN->Click "Encrypt Smartphone"

What is the current behavior?

Device shows for 2 seconds green Android Screen and switches instantly to e-Startscreen

What is the expected correct behavior?

I do not know, probably some more time spending for teh encryption and a restart wich shows afterwards: Device encyrpted. or sth ;-)

Tried with 0.7-o-2019101126867-dev-starlte and the newest Version 0.7-o-2019112632032-dev-starlte

I tried with my Fairphone 2 with 0.7-2019112732147 and the behaviour is the same -> No encryption possible.