Set polling to 60 minutes, but the monitor is polling twice an hour.

Set polling to 60 minutes, but the monitor is polling twice an hour.

I have set up a Web Services Monitor as follows:
  Edit Monitor
    Polling Interval: 60 Minutes
  Configure Alarm
    Poll 3 times consecutively before rporting monitor is down
    Poll 1 times consecutively before reporting the monitor is up
  SOAP Request includes this parameter:
    ser:checkHealthTimeInMinutes=60

However, I am getting alerts at both 54 minutes after the hour and 26 minutes after the hour.

Also, the WSDL response time graph shows events occurring twice an hour at roughly those times.

Also, the Monitor Information window shows a changing "Last Polled at" and "Next Poll at" time keeps switching the next poll time to either xx:26 or xx:54 (the next poll is always shown as 1 hour from the current poll, but the next poll really happens roughly every 30 minutes)

How do I get the polling to just run once an hour?