Hi, what make of brakes and levers do you have? If it is vintage then by now it could have anything on there.

My suggestion is that if you are having a problem with the suicide levers, given that it is an old bike, it might be a sign that you need to overhaul the whole brake system. When well set up they work, but if they are blocking the brakes you might need new cables, new pads, re-adjustment of whatever brakes you have and, potentially replacement of the whole levers and/or brakes if they have worn.