Always leave it in USE except when storing the RV without plugging it into Shore Power (SP)
In the two years I have been on this forum I am sure the Store/Use switch has been the most popular fix.
To deminstrate how misunderstood this switch is, we were told at our PDI to "turn that switch off every time you leave the coach". It didn't take me more than 10 minutes on this forum to learn that just wasn't correct.
2017 Gemini 23TR Ford chassis w/ power stroke 3.2
DW, Daughter and 2 dogs, Sofie (black lab/boxer) and Phoebe (schnoodle)