Cassette players are inherently problematic because they require that the cassette tape be pulled between a set of rollers by a capstan shaft before being wound on the take-up reel. The capstan shaft and rollers can become dirty from the tape flaking off on them during use. This causes the capstan shaft and rollers to become sticky and the cassette tape to get stuck and wind around them. Cleaning the capstan shaft and rollers on a cassette player ensures that tape passes smoothly through the rollers instead of being "eaten." The repair can be done within a few minutes and doesn't require disassembling the cassette player.
Remove the batteries from the cassette player and disconnect the power cord from the cassette player, if present. Put the cassette player down on a table. Eject the lid. Remove the cassette tape, if present. Carefully unwind the cassette tape from the capstan shaft or from the rollers, if wound around them.
Blow out the cassette player with compressed air. Dip a cotton swab in rubbing alcohol and hold it till there is no dripping from the cotton swab. Rub the cotton swab against the capstan shaft while gently rotating it from the top with your fingers. Repeat this process with a second cotton swab. Stop swabbing when the capstan shaft is free of any debris.
Replace the batteries and the power plug, if one was being used. Insert a cassette and close the lid. Press the "Play" button on the cassette player and listen to the tape to make sure it is running correctly.