955i Gearbox Problem

Hi all, my 1999 sprint st 955i has a gearbox issue. When I’m in third and want to change down to second sometimes it goes into neutral, and the neutral light comes on. When I lift the lever it goes into second. I didn’t think these gearboxes could over select, at first I thought I was having a blonde moment and thinking I was in third when I was actually in already in second. I’m new to this bike, but I’m sure I’m in third and not second, and therefore it’s faulty. Can anyone suggest a cause?