C# (Xamarin) WaitHandle.WaitAny returning Int32.MaxValue (0x7FFF FFFF)

Question

The documentation for WaitHandle.WaitAny Method (WaitHandle[], Int32) says it returns "The array index of the object that satisfied the wait, or WaitTimeout if no object satisfied the wait and a time interval equivalent to millisecondsTimeout has passed" and in the Assembly Browser I see that WaitHandle.WaitTimeout is 258.

So why do I sometimes get 0x7fffffff (Int32.MaxValue) as a return value from this function?

Is this a known bug in WaitAny(), or just a line missing from the documentation?

ADDED LATER:

By the way, the error happens a couple of times, then goes away, without me doing anything to "fix" the handles or anything like that.

Microsoft Documentation

Xamarin Documentation

Code:

class CommandQueue
{
    EventWaitHandle m_abortRequest = new EventWaitHandle (false, EventResetMode.AutoReset);
    Semaphore m_commandCount = new Semaphore (0, 10000);

    public CommandQueue ()
    {
        m_processTask = new Task(() => Process ());
        m_processTask.Start ();
    }

    public async Task Process()
    {
        WaitHandle [] handles = new WaitHandle [2];
        handles [0] = m_abortRequest;
        handles [1] = m_commandCount;

        for (;;)
        {
            int wait = WaitHandle.WaitAny (handles, 500);
            if (wait == WaitHandle.WaitTimeout)
            {
                OnIdleTimer ();
            }
            else if (wait == 0)
            {
                // SNIP: Code to handle a request to abort the processing of commands  
                break;
            }
            else if (wait == 1)
            {
                // SNIP: Code to process the next command in the queue
                await Process(nextCommand);
            }
            else
            {
                Debug.WriteLine ("*** Unexpected WaitAny(" + wait + " = 0x" + wait.ToString("X6") + ")!");
            }
        }
    }
}