NOx Sensor bank 2 Sensor 2

Hi, have a 2015 GC ecodiesel with an intermitent mil code P229E NOx Sensor bank 1 Sensor 2. What is unusal is this code has reared it's head when in a car wash or driving in heavy rain now about five times. As soon as dryness comes the MIL goes turns off, very often within a day or two. Given the symptom, I had a very good shop undo the two sensor connectors hit them with contact cleaner and put back together with dielectric grease. two days later in a heavy rain and driving, the lamp came on with the same P229E code

Any similar experiences or possible causes? I hate to replace the expensive sensor to only find out it's a different problem

Thanks
Brian