I completely uninstalled nodes. Any way, going forward with my activities, at the moment I can't restrict the issue to specific node
Hopefully by today COB I'll be able to write more.
I'm here again. I completely recovered my 4 flows with all relevant nodes (I've installed all them again). Then I've done some check; restarted node-red, rebooted rpi... every thing is fine. Inject node works properly.
At this point I can suppone that something was wrong in those nodes which hadn't an instance in the flow...even if this sound a bit strange.
Those node were the following:
In case of news I'll let you all know.