The IR receiver can generate false IR strings when there is high frequency distortion on the 5V supply. This depends on the system, some have it extremely, others not at all.
For the A version: cut the PCB trace wich provides 5V to the IR receiver, add a 100nF capacitor between the 5V and GND pads on the solderside of the PCB. Add a ferrite filter on the component side of the PCB, connect one side to the 10 ohm resistor and the other side to the 5V pin of the receiver. Have a look at the Uirt2A picture, this will clarify it.
For the B version: Add a 100nF capacitor between the 5V and GND pins. You can use the same ferrite filter as above or slide a ferrite bead over the 5V wire of the receiver. The kits and assembled units will contain the cap and either a filter or a bead. The pictures below show what I mean.
