I've found (well, in fact - no, I didn't, my 7-year old Bug Hunter William did) that this is not just the Ogg Decoder, it is sometimes also the case with the WMA and MP3, indicating it might actually be something other than the decoders themselves, but something else in the player software structure.

Quick convenient fix to stop this: before you turn your ignition off (assuming your ignition is properly wired, of course!) press PAUSE, then SLEEP, then IGN off, then wait until your power off timeout expires before removing the player unit from the sled. I have set my power off timeout to 5 seconds as a result.

Oh, and by the way - I didn't even work out this fix MYSELF - William did: if ever there is a software engineer in the making, this 7-year-old is IT. I am appalled, and at the same time surprised and gratified that I seem to have some influence on the gene pool. What's worrying is that a 7 seven year old with zero training is better than I am at bug observation/fixing than I am as a professional software engineer with some 20 years experience behind me!! Jeez.....