If you are in sneak mode, you have to turn it off first.
This doesn't happen automatically when you switch to another 2ndary hand skill, you have to turn it off yourself. So first select it, then (with as leader (golden box) the char that has sneak mode set to 2ndary hand skill) right click, thus undoing the sneaking. Only then should you switch to a different secundary hand skill.
Is it just your main char that is stuck in sneak? That would be pretty weird, since both the lead chars usually have the same sneak setting.