My Technics MD player/recorder will not play some of my home recorded MD,s?

My Technics MD player / recorder will not recognise some of my home recorded MD,s and shows "DISC ERROR" Recordings were made on the Technics equipment and until recently MD,s played OK.The same MD,s still play OK on other players I have.
I have tried a TDK MD lens cleaner but this has not helped, although lots of my other MD,s play perfectly well on the Technics system.
Is the problem with the MD or the Technics equipment.
Do MD,s have a shelf life or can they themselves become defective? Any help would be appreciated.