Had a similar problem using FHEM as controller. A downgrade of the board-definitions within the Arduino-IDE to version <=1.6.11 helped to some extend:
The rebooting issue is gone, but the status within FHEM no longer goes to "connected" but sticks in "startup complete".
Additionally:
Someone in the FHEM forum reported lost messages using FHEM as a controller and a serial GW. According to this report (https://forum.fhem.de/index.php/topic,60917.0.html) he used two computers and two GWs to compare the messages he received (other controller was MYSController).
In my setup, I may also have some problems that could be related to that:
One of my nodes has (amongst other things) 6 DS18B20 attached. When using a loop to read all the 6 and send the temps immediately, I do not get reasonable values for the 5th and no temp at all for the 6th. But this can also be related to other reasons (wiring, power source, NRF), I have to do some more testing on this to be sure.
(Using 2.0.1-beta and Arduino-IDE 1.6.12 with board-def for Nano 1.6.11)