We upgraded code to 6.0.188 on two mesh controllers and here r the observations..
After the code upgrade one of the controller after probably 30 mins rebooted and was not reachable. Console access showed the config script. This controller has LAG enabled. Looks like the code upgrade wipes out the LAG info or the VLAN Tag so the controllers are not reachable.
The second controller was not in LAG. This one after the code upgrade displayed a web based dialog. I was able to key in the values and was back in business.
So if you have remote controller and no way to have console access it is better to disable LAG so u will have access after the code upgrade enable LAG. This may depend on the code base you are going from.