Firstly can I ask how you got on with the loudspeaker problem as you raised in this thread?
https://forum.beoworld.org/forums/topic/beocenter-9300/
With regard to the BC9300 CD door, can you still hear the motor running when the door tries to open? If, so, either the mechanism need cleaning and lubrication or the drive belts need replacing.
A service manual is available on this site for Silver/Gold members, and you can buy new door drive belts here: https://www.beoparts-shop.com/product/belt-for-sliding-doors-beocenter-8000-8500-9000-9300-9500/