Pyramid PR530A 2 Channels Receiver "volume pyramids" Questions

Porsche cdr22 volume increases and button will not dcrease The volume increases by itself I can be driving and the volume increases and display changes 17, 18, 19 etc. when I try to decrease volume ...

Master volume control knob The knob does not have a stop but keeps turning after it gets to "no sound".Same for maximum sound. Is this normal? If not, is there an easy way to fix it? Thanks, John P. ...