I'm pretty sure the reason why the R6400.chk file (Kong mod) will not install is because the v1 and v2 have different board ID's. For the v1 it reads U12H332T00_NETGEARHDR0 and for the v2 it reads U12H332T20_NETGEARHDR0 so that is probably the reason why the firmware is rejected on the v2. The Kong mod has the v1 board ID implemented so it won't work on the v2, only on the v1. Technically the mod will run on both routers though.
I am not sure if it is as simple as opening the R6400.chk file in a text editor and changing that one number and save it.
Can any of you experts out there confirm if that is the case ?
On that note... the firmware that Netgear posted on its OWN website for the R6400v2 also has the wrong board ID, so I don't think there is a way to flash the original firmware back onto the router.
v1 board ID: U12H332T00_NETGEARHDR0
v2 board ID: U12H332T20_NETGEARHDR0
The file that Netgear posted under the v2 version actually has the v1 board ID in it.
Was about to install Kong on 6400v2, having second thoughts, don't wanna brick it. Did you have any luck with that text mod? Were you able to get it back to factory?
I posted another way of doing it. It’s how I did it myself (before I did all this “research”).
https://www.myopenrouter.com/forum/update-installing-kong-build-netgear-r6400v2-workaround
I hope that helps... eventually I am sure this issue will be addressed in a better easier way.
I managed to flash back to factory firmware today. Such a pain. There is no build for the 6400v2 right now that really works great... also, the board ID is actually U12H332T30_NETGEARHDR0