Linksys RE6500 revert to stock firmware

Hi.

I want to revert a Linksys RE6500 back to stock firmware. When I try to do it using the TFTP flash method which I used to install OpenWRT it doesn't revert back to stock. It also doesn't revert to stock when flashing the oem firmware from within OpenWrt (Luci).

In both instances it loads the firmware but doesn't overwrite OpenWRT. When I try to open the config page in a browser I see an "Emergency Firmware Upgrade" page that prompts for a firmware file. Each time I've selected the OEM file it doesn't overwrite OpenWRT either.

There is no information on the Linksys website that addresses this situation.

Does anyone have any other ideas that would help?

FWIW, I opened the RE6500 and discovered there is no serial pinout. That was going to be my next try. There should be one according to this forum archive, but it must be info on an earlier production run of the unit. The holes are in the board, but no pins are there.