We soon realised that the previous PCB design was inadequate because the presence of the ground plane copper all around the solder pads and traces meant it was very difficult to solder without shorting. Although the soldering had been completed, it was laborious, and also meant the final product was easy to damage. It was decided to create a new PCB for the IR sensors because of this, with no ground plane and the ground connected simply with a trace, and to remove 2 of the sensors found on the original PCB (the two 'rear' sensors) leaving only 2 front sensors.