Thanks for replies. Here are some photos of the installation and I can see now that the LED oblong hole has been cut by the installer. Very professional job too. here's some photos...
1. must be the electronics
2. Obvious what this is
3. Wires behind the LED
4. Same as 3 from a distance
This issue is also on ST-owners.com and I've been sent the GPX User guide with instructions on re-calibration.