Oh ok, than I misunderstood, what’s gonna be fixed.
It’s not just custom device handlers. I have the same symptoms to this FAQ
Another piece of information with a solution could be found here in the latest 7 posts.
I already told about this to cbaumler and Kianoosh_Karami, but third time the charm 
I also asked RBoy if the device handler is implemented correctly with the latest changes in mind.