Slash voices keep changing voice number

As I move around adding slashes here and there in a guitar part, the voice number of the next batch of slashes keeps incrementing unbidden by me. It’s not a big deal, but I don’t understand why it needs to do that.

It sounds as though you’re using Shift-Alt-V repeatedly, which is the command for creating a new slash voice. The command for scrolling through existing voices on a staff is V.