Hitachi FX850E - Won't accept tape?

Hi, I have a Hitachi FX850E. Worked fine till yesterday. insert / eject was fine. Now, trying to insert a cassette, carriage does not automatically take cassette. Does not drop down into play position. I can force the tape all the way in, but carriage still does not drop. Eject works in the sense that the cassette is pushed forward again. It seems the whole mechanism of the carriage movement down to play position is failing. What could be the problem, and could I fix it?