One thing I noticed when the CDs played was that after installing the CD cartridge, the player was scanning from bottom to top and what looked like a laser (it was red) was lit as it scanned, when it was done it went back down to the bottom (ie CD #1)
I tried it again this morning and this time I didn't see the laser and when it was done scanning, it stayed at the top.

BTW, how do I check that the CD player unit is set for the correct mounting position (vertical or horizontal) other than visually looking at it? Is there is switch? Visually looking at it, the CDs are installed horizontally.