True. I am not doubting it can happen- if you would only rely on a single computer with no further po2 monitors and ignore best practise concerning sensor swaps. Bit still- having limited cells showing same value is rare if not very unlikely.
http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf
http://www.revo-rebreathers.com/wp-content/uploads/2016/02/Understanding_oxygen_sensors.pdf