I know this is an old post, but I have been struggling with this issue and finally found the fix, which was simple at the end of the day. I thought I had cleared all of the conflicting inputs that were tied to my +/- keys. While in BigBox, I had to go to the Menu>Options>Keyboard Mappings. It was there that I saw (far down the list) that there was a "Zoom In" and "Zoom Out" command tied to the +/- keys (the same that I use for my volume controls. As soon as I cleared those out, the problem was fixed! Y'all probably figured this out long ago but figured I'd share in case anyone ran into the same trouble I did.
