1998 Hiace Super Custom Stereo - error codes?

I've got a 1998 Hiace Super Custom Limited Edition (3L turbo diesel) which has a Toyota Brand (RN-3000) radio/cassette with a CD player, linked to a 12-CD stacker in the rear of the van.

Just recently I've started getting intermittent error codes when loading a disk. "Err 1" is a common one. When that happens I load a different disk and then can sometimes re-load the "faulty" disk successfully.

Today for the first time I got what seems to be a more serious "Err 3" and NO disks would load. However, after switching off the van for a couple of hours, the system came back online and was back to the intermittent "Err 1" situation described above.

Can anyone point me at a list of error codes and their respective meanings?

Thanks in advance.