Just read the following article about some minor modification of Inspro,
http://www.nobubblediving.com/inspirationpuffer.htm
Int it author claims around possibility of appearing thin film of water like soap bubble over galvanic O2 sensor rendering it to fail to read correct PPO2.
I.e. there is a need to clear away the vapor from sensors.
Way the author offer solution to this problem is to make some kind of diluent puffer over all three cells.
Did you consider any possibility of this situation being happen in O.R. rebreather, and if yes, how do you plan to deal with it?