R610 is continuously rebooting after upgrade upgrade

[sunilw04]

Hi

I have 3 APs - R610, recent software upgrade to 200.15.6.212.20.  One of the APs is not joining the mesh and it is continuously rebooting. It looks like it is getting connected on the network and trying to join the Mesh. I get this message when connecting to its IP address:

"Building the Unleashed Network. It may take a few minutes."

Then, it reboots again. I tried to reset it many times, but it keeps into continously reboot cycles. Any ideas on how to fix this.