The clock exact frequency isn't critical, seen units that were outside the specified interval and still worked fine. It has to be off by a lot to actually cause issues. In regard to the motor, note it can be tested outside of the walkman. Refer to page 8 of the pdf service manual (pages 11, 12 of the actual manual). To test you need to connect pin 3 to B+ and pin 4 to B+/GND (clockwise/counterclockwise rotation) through a 4k7 (or higher) resistor. After you get the motor running, check that when motor is stopped by hand, the current draw is ~250mA. If not, perform the adjustment at page 8. Also motor should be able to start again on its own after it's released, even at 1.7V B+. As a sidenote, these disc motors don't have a lot of torque, so the finger feel test is only relevant if you know how a good one should feel. Regarding the unit stopping, if "stop" means the mechanism unlatches it's related to lack of reel rotation signal. If the sensor is faulty you can take it from that JX505 donor you used before. If however just the motor stops and mechanism remains engaged, it's a logic control problem.
