Problem with DVD player on home theater

I have a strange problem with the playing of DVDs on my Magnavox home
theater system. Sometimes when playing a disc, towards the end it
just freezes or slows to an absolute crawl, as if it were going frame
by frame. I have taken the cover off and cleaned the lens and both
cleaned and lightly oiled the 2 rails, but it doesn't seem to have
helped. It doesn't appear to be scratched discs either, since it
seems to happen at the same point on the disc, no matter which one is
in there. Any ideas on what might be wrong? Thanks for any help you
can provide.