TP-Link 840n v5

The firmware for this router is available here in snapshots.

It is a sysupgrade only image. I have tried it and the Wifi strength is less than half as compared to the original firmware.

All my best attempts at changing the region and increasing the transmitting power have failed.

Has anyone come across an issue like this, that has a quick fix? OR has it got something to do with the driver or hardware etc etc?

I have a couple of these routers and am desperately trying to get them to work. Any help would be much appreciated.