I found an error with this tool if you are trying to switch parity on a road layer and you have the road layer in the map twice with the same name in the table of contents. This will make it switch parity on all roads.
I found this out because I often add the same layer to a map multiple times and just symbolize it differently. If they are named differently, it is not a problem even if they point at the same layer.

Has anybody resolved this yet?