Controller disconnects when moved away from console

Hi All - I’m trying to fix a controller for my friend. I’ve successfully fixed many of these but this has me stumped. The controller will sync fine when placed very close to the console but disconnects when moved a foot or so away. I tried his Xbox and mine so I know its not the console, plus other controllers work fine on both xbox’s. I also connected to a PC both via bluetooth and the wireless USB xbox dongle and am having the same issue.

It seems like this controller has a bluetooth range of one foot. I made sure the wireless antenna cable was securely attached inside the controller, even checked with a multi-meter to ensure continuity between the controller antenna and the spot the wire is soldered on the board. Short of telling my friend he has to use this controller with a cable, how can I fix this?