Default [Q] Erratic GPS

The GPS in my Nexus 7 has suddenly become VERY erratic compared to all my other Android devices. This device is fully stock, up-to-date and I did a factory reset just to see if something had become corrupt. I've also downloaded "GPS Test" app and I can see the signal strength is pretty erratic- one second I have 9 satellites, the next second I have 3 and the signal strength never seems consistent compared to other devices which I'm testing at the same time and the accuracy is always much higher than the other devices. It also takes a several minutes for the device to lock onto satellite signal while the other devices take only seconds. I thought the problem could be related to the antenna, but I rigged up an external antenna by hooking it up to the GPS contacts and its still erratic.
Does anyone have ideas as to what could be causing this or an idea of something to try as a fix?