Upgrade My Cloud to Twonky 8

ATTENTION: I have to report a heavy bug after updateing to custom edited firmware 2.30.165:

Yesterday I wanted to create a new user. This has still worked. But all functions for sharing and assigning rights no longer worked.
Also different admin functions no longer run. Cloud settings and device names can not be changed anymore.
After the installation of the original firmware everything works again normal.
The exact cause I can not determine.
Whether the other v2.xx.xx devices is synonymous so, I do not know.