I seem to have fixed mine, fingers crossed. After investigating pretty much everything, I re-soldered the solder joints on the heated plate - both at either end of the sensor and all 4 along the connector strip. Soldering iron set to 470degC, as it feels like high temp solder.
All the joints looked OK visually, but re-wetting them seemed to fix the problem - for now anyway.
I detached the wires to do this and of course re-attached into the terminal block, so it may have been a fault with a screw terminal I guess, but I'd checked that before without success.