I have a braun 450 watt / 220v stick blender that has a detachable blade with cup and also a separate food chopper that it can attach to. The blender runs, but will not work to mix up food. It feels as though it is slipping and it makes a high pitched whirring noise. How do I fix it? It is a little over ONE year old. I had a stick blender for 25+ years in the States and never had a problem.