Added the resistor but no change. I also tried different capacitors but no such look. My code is basic at the moment just on/off so the problem could be solved in code. I think only the immediate temp measurement after control input is unstable, thus pushing off the whole oversampled set of data.
I am now switching to a one wire temperature probe as it has increased resolution and is in a proper package. Any further problems will likely be solved in code.
Thanks for your help guys.