I recently bought an aftermarket Aux in adapter for my RCD500. All installed and working fine.
The other day, I ejected a CD ready to load another. I went to load the new disc in but all it did was take the disc in, then out, then in, then out (then shake it all about) and then promptly displayed "ERROR - SERVICE".
Now, I'm concerned that the Aux in adapter (which emulates a CD changer) has sent some spurious signal into the head unit causing a mechanical issue. I removed the aux adapter but still the problem persisted.
A day passed and after a period of inactivity it seemed to fix itself... I managed to eject a couple of discs and re-load them. So all seems fine.
I'm going to put the aux adapter back in today to see if this problem happens again.