Ah ha! I took a close look at the end of the data cable and it appears the six tiny prongs on one end are bent out of alignment, and one of them is missing. I’m now using my retractable cable that I normally just ust for travel; we’ll see if that solves the problem.
I will still follow your advice to open up the player and vacuum out dust and debris, though. It won’t hurt. 
Thank you!
