The only viable solution to this problem is to get yourself an Asus or Netgear Router because unlike these incompetent morons at TP-Link, Netgear and Asus atleast has decent customer support to...

@aTOMic1971 Wow. Ok I will turn off IGMP proxy and see how it goes. Thanks for the suggestion.

@Mare007 Is it possible that the firmware physically fried the 2.4 Ghz band?

Has anyone tried flashing Archer A6's firmware on C6? Both are same device.

Nah it has nothing to do with the crashes. I tested it without WDS bridging and it still crashes.

@Kubas Do you have any router in bridge mode on the 2.4Ghz band? Channel is grayed out only when you have WDS bridging enabled as both the routers needs to be on the same channel.