Hey guys. I recently got the Logitech Z5500 speakers. I love them to death, but had a quick question for other owners. I notice that when you turn the volume knob on the control center, it will get loose, then tight, then loose, then tight. It almost feels like it is rubbing against something on the inside. Although, I did notice that it rubs around max volume and around min volume. So, is it meant to do this, or is mine defective?