Have a good read of this thread about the door strings: https://forum.beoworld.org/forums/topic/my-beocenter-9500-restoration/
And the Speaker 1 problem does usually indicate that it is time to replace the Mute relay – the contacts are corroded or dirty – best to replace. You can find a new one at BeoParts.
EDIT: I managed to get some replacement door strings from this seller but I think he only has the plastic sliders left: https://www.ebay.co.uk/itm/166490477922
Location: Warwickshire, UK
My B&O Icons:
