I read this post yesterday and today I solved it.
My GW was restarting as soon as I was sending a command to a MYS node with dimmer child.
I am using nRF PA-LNA, with extra power supply, PA_HIGH. Domoticz 3.8795, MYS 2.1.1. Nano as serial GW.
Tried PA_LOW, new nRF but that didn't help.
Today I found the solution, I disabled DEBUG in GW and now I can't reproduce any restarts.