@Daniele That is the opposite of what I have - here my GW is 'up' in mycontroller but node 0 is 'down' and yet it is working perfectly with myc and all nodes!
If this is a random thing I would suggest triple checking all connections individually to ensure they are tight and no movement at all can happen. I took out a DC barrel connector and replaced it and things got a lot better from just that one change.
I also put the arduino watchdog on the GW node as another way to recover from any 'hangs'.
I added the previously posted operations as another way to tackle problems with the gw, but not sure how to tell if it is working as expected!
Finally I upgraded the pi from stretch to buster and fully updated everything.
Since then I have had 7-8 weeks without any issues (previously 1-2 weeks was about all I could hope for).
I still have a ups on my to do list. That will happen soon I hope.