Oxygen probe showing poor saturation

Last night we had problems with the blood oxygen saturation monitoring machine. It kept on showing results that were clearly too low for what was actually going on with Raphael. We tried a few things:

1. We tried retaping the probe to his foot a few times. If anything this seemed to make the problem worse. At one stage it was showing a "reliable" signal but only reporting a O2 level of 15%.
2. We tried using an old probe. This was even worse, at one stage reporting as low as 3%.
3. We tried reseating his mask again but this had no effect.
   
4. We then attached a brand new probe but this still showed saturations dropping as low as 60%.
5. Eventually the computer techie side of me took over and I checked all cables only to notice that the machine end of the probe cable was loose.

Finally after reseating this cable everything sprang back to normal, well nearly normal anyway. It only showed 92% O2 level which isn't great but it was good enough for us to call it a success and we finally got to sleep at around 12:30.