Peter,
I have the Nu-Temps and had the same problem as you with the haywire probe. I took the probe and placed it over one of the furnace vents (it was winter) for a couple days, then tried it again and all was fine. They don't handle moisture in the braided wire well. My next move was to order the eyelets from the BBQ Guru folks so I no longer pinch the wire between the lid and cooking chamber. WSM Eyelets
I have the Nu-Temps and had the same problem as you with the haywire probe. I took the probe and placed it over one of the furnace vents (it was winter) for a couple days, then tried it again and all was fine. They don't handle moisture in the braided wire well. My next move was to order the eyelets from the BBQ Guru folks so I no longer pinch the wire between the lid and cooking chamber. WSM Eyelets