With the latest update to Ver 1.0.24 I have noticed when changing bands "sometimes" Slice A would just disappear. Nothing on either side of the display and nothing at the center. Most of the time clicking +RX brings it back but one time it did not and I had to reboot the radio.
It is band level persistence. If you never had a slice on that band and you change to that band, you will need to create a new slice. This is a behavior change from previous versions of SmartSDR. If you have a 6500 you may be out of slice resources when you change requiring you to create a new slice.