occasionally, the clock starts a double 'beeping' that increases in speed until it's an annoying stutter of beeps that continues until I hit the 'power off'/'alarm reset' button on top. This is not a preset alarm time and I make sure I have pressed my 'alarm off' button when I wake up to a preset alarm time. This isn't a routine occurrence so I can't figure out the pattern. any suggestions on how to stop this?