I have the same deck. I noticed that it eats takes when I hit the monitor button (back and forth, monitoring the recording). It doesn't happen every time, but enough that it has eaten a good share of tapes.
There may be slippage on a belt or clutch for the take up spool hub. I think if you take a look at the cassette mechanism you will probably conclude that it's virtually impossible to fix these things, especially as there's a lot of plastic in a warm working environment that ages it eventually.
