Any cassette deck will need service over time due to perishable rubber parts such as belts, idlers,and pinch rollers. Parts like capacitors change value with age or leak.
Parts for many cassette decks are not available, too expensive. or bad quality. Restoring one is not cheap and only worth while on the top of the line models. Not a simple job either.
If you have tapes with content that can't be replaced then it might be time to rip your cassettes to computer files. Audacity works fine. FLAC files are lossless so the file will sound like the tape.