I didn’t want to post everything, was trying to isolate problem. Seems found it:
_serial is Serial1
What I am doing here is stopping serial1, powering off serial device, powering on serial device and restarting Serial1
This fires when Serial1 stops receiveing data meaning my data source died because of something - this happens and I need to deal with it.
So this code should “reset” Serial1 and apparantly is dying on new firmware version. It was working on older ones.