Why does my Panasonic RX-DT55 cd player stop mid-track?

Reni, it is possible that this caused by a mechanical failure or your CD servo. You may have to take the unit apart and take a look. Once apart, take a look at the spindle motor and clean all the part. the spindle motor would be the most likely reason for the "running out of steam". With a unit that has that many years of good service, sometimes a good cleaning is all that is needed. It all depends on how handy you are as well, since there are a few mosfets ad power transistors that can be at fault. For the CD playback they are IC701-IC705 that may give you issues as well as R701:-) You should find those numbers on the PCB. Hope this helps to at least get you started. Good Luck.