My router will not boot after upgrade. I get loading kernel from nand.. starting services and the router will not boot after that.
Dave
Welcome to my world. 
I had 3 1009’s and 2 1016’s do this.
It seems that it was something in the config that was killing it. My 1009’s rebooted at “starting services”, my 1016’s just hung.
I ended up going back to 6.15, then doing an “/export compact file=backup”. Then I cleaned out the export, leaving only what I truly needed. Then did a copy/paste section by section, cleaning up errors as they happened. It took me a few hours for each one.
The upgrade went so poorly, what I now have one of each CCR on-hand. I am upgrading the units in my office, then swapping them in the field.