I had this "high pitch" issue a few times. The high pitch does not seem to be indication of vibration motor permanent damage. The motor just get stuck (maybe because of dust). Each time I solved it by:
1. Start vibration by script (it is somewhere in d-bus wiki).
2. Hold the device and hit with it my second hand with various positions.
3. Repeat until high pitch is gone and vibration is strong.
4. Stop vibration by script.