Non working cassette. Not too bad to change the belt, but often the support shaft for the flywheel is broken and can not be fixed without replacing it. It's made of weak pot metal

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Sliders, if they are uneven volumes or cut in/out - not good.
Music search. If you want to use it, make sure it works. If not working, then it probably never will.
If the function switch/power switch don't work, often just cleaning them will clear things up.