So I test and test, I add and remove regularly nodes and gateway, MyC and put to the test, but it holds good
Well, today I had to start over on a clean beach, a clean reinstall, the ghost nodes did not want to leave
after 2 hours still nothing on the node55 (test reset reboot)
I reloaded the sketch and MyC recognized the 55!
I have had 'ghost nodes' in MC ver 1.6.0 - These are nodes showing in the list that do not exist in real life. I am hoping that a new SSD sata to USB adapter has cured this for me. Note I also went from 2 gateways back to one. Even with external power supply there was still an issue on booting with both gateways attached.
If you are testing a lot of things please remember to use the mysensors 'clear eeprom' before reusing a node or gateway, it can cause issues if previous data stored in there (like routing table) are not removed before re-flashing. Maybe you already do this, but is worth mentioning anyway.