I am unsure of the full symptoms you have been experiencing but I had a problem with a boot mounted 12 disc stacker showing error after the discs had tried to load, I removed the stacker and on investigation found the main drive cog for the loading of the discs had stripped a tooth, because this drive cog only turns through 180 deg the fix was simple just realigned the cog so the stripped tooth was not used any more. It is a reletavily easy job to do yourself just be sure to refit the tension springs all round the cd player when putting back together.