QTimer often freeze and miss timeout signal

My code like these:

self.intervalTimer = QtCore.QTimer()
self.intervalTimer.timeout.connect(self.loop_do_run_action)
self.intervalTimer.setSingleShot(True)

def loop_do_run_action(self):
#do some actions
....
self.intervalTimer.start(1000)

I found the QTimer often miss timeout signal, and the loop_do_run_action often can't be called, then the loop will be stopped. When this issue happened, I call self.intervalTimer.isActive(), the result is True, but the slot never can be called.