There are two reasons why the handle will not stop spinning. There is no exact way to determine which of the two is causing the problem. One reason could be that the threads on the stem are damaged. This will cause the handle to slip, and keep spinning. If it is the the threads on the stem this can be fixed by replacing the stem. It could also be the threads in the faucet itself. If it is the threads in the faucet, the complete faucet will need to be replaced.
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