First before upgrading enable new devices Setup -> Settings -> enable "Accept new hardware devices" Don't forget to click "Apply settings"
Then upgrade! That's was it all, at least for me. Hopefully it works for others too.
Reason:
With OZW 1.6 new devices are created. In my case a lot of devices with the name "Previous Event Cleared"
Device as Fibaro FGMS001-ZW5 also create a few other devices.
Initially every battery powered devices has to wakened or included again, those devices with all zero's in the Zwave overview.
You have to check if every hardware device has an accompanying device with 2 zero's at the end of the ID.
If not, select the hardware device in the Zwave overview and click on "Refresh Node Info" Be patient.
Wait until the 2 zero device is present en proceed to the next until all hardware devices have a device with 2 zero's at the end.
Some devices already have such a 2 zero device from OZW 1.4, mainly the battery powered.
Leave the "Accept new hardware devices" enabled because some devices come after sometime with an extra device.
In my case I have an "Shenzhen Neo Electronics Co Ltd Siren Alarm+" Siren and the extra device came after more then 12 hours.
THATS ALL.

The fact that I did not discover earlier is that I am surrounded by a lot, I mean a lot, of neighboring device belonging to someone else.
I do not want those so my setting are always disable "Accept new hardware devices"
I once had it enabled and it went fine for a while, but I did not know how long to wait for the last device, see my siren.
So I disabled it so soon and got into the error again.
I believe that the fatal error is coming from the fact that a value has to updated on a device that does not exist or that the device could not be created. This is a challenge for the developers to find out and correct.
