I had your problem and more. E5 errors, also, and the OEM changer finally got to the point that it would not play a CD completely through. I took the changer out, took off the top cover, face plate and bottom cover. I used a tube of TEFLON based lubricant that I got from Radio Shack to lubricate the chrome rails, the nylon gears, screw shafts and anything that looked like it might move. I was careful not to put any in the path that the CD travels.
I noticed that the laser beam travels along a rail and is driven by a screw & gear shaft. I turned the gear to move the laser where I could wipe it off with a dry q-tip.
I re-assembled everything and reinstalled the changer. The changer automatically synchronized itself.
That was about a month ago and I have not had any problems since. First time I have gone this long with no errors in about four years.