CD load problem

in-car unit, now intermittently has cd-loading problem.  When empty, will suddenly attempt a 30 second eject, after which it won't trigger to pull in a disc.  Sometimes turns itself on specially just to eject the non-CD!  When CD source is selected it says "press eject" (even though empty).  Also sometimes, when CD loads seemingly OK, will continue clicking after it's in, then does the 30 second eject business again and off we go again.  Seems to change its mind eventually if left alone (so far, anyway...)
The unit is much modified (see PWB Electronics - www.belt.demon.co.uk) and sounds fab, so I want to keep it!