This is the best help forum I've seen for CLD-99 issues. Hoping mine might have a solution.
I trade favors with a fellow audioholic at work, and he's got a CLD-99 that occasionally locks up with the E3 error after playing an audio CD. When it occurs, the CD plays to the end of the final track, and the laser carriage, instead of parking, immediately withdraws to the back of the unit and jams on the LD tray stabilizer bar. After a couple seconds the carriage motor shuts off and the E3 error displays. If the unit is powered off and the carriage assembly is manually moved forward, the unit will reset and operate normally on next power-on.
Here's the trick: the unit may cycle through dozens of CDs, pressed or burned, without a problem. A blank CD-R won't crash it, and neither will a badly-scratched disc. My coworker took it for service twice and they couldn't replicate it, so it was cleaned and returned without a solution.
I finally found a disc that would crash it about 75% of the time: Fields of Gold, Best of Sting 1984-1994. The only unusual factors are a longer-than-average runtime (1:06:33) and a final track that ends on the minute (5:00).
At first a limit switch seemed like a possible culprit but I can't see one in the carriage path at the time when the failure occurs. Some other sensor? Firmware bug?