Our 2015 Tahoe GPS just started showing the wrong position. It has us about 40 miles off, and, in the upper right of the screen are the letters "GPS" with a red X through them. . Also, the vehicle does not recognize my iPhone 6 anymore. I've read where there might be issues since 3G has been replaced by 5G but no one else I've talked to is having issues with theirs??? Also, GM has a GPS update for about $150 but I can't find out if it covers that issue. Does anyone have helpful suggestions?