Both my neighbor and I have very similar pools, same equipment, same PB. We have very hard water here in southern AZ, so almost everyone has a water softener. When my house was built a water softener loop was plumbed in, so that all outside taps including my pool filler are untreated water.
My neighbor does not have this, so his outside taps are soft water. During a filling of the pool he can use the one connection on the front corner of his house that has untreated water, even if he didn't, the capacity of the softener would quickly be overcome and most of the water would still be untreated.
Here in the middle of the Sonoran Desert, with daytime temps over 100 and humidity from single digits up to a high in the teens, we have a lot of evaporation and his auto fill is constantly putting soft water into his pool.
His SWG shutdown indicating high salt. Could this be due to the soft water? Are there other issues could be caused by the soft water feed to the pool?