I experienced these on both of my PP annual calendar, 5960 and 5726. I bought both on the same AD and I assume the technician who set up both is the same guy. The month ring didnt change at the end of the month on the 1st time. On 5960, after I myself adjusted, all is fine. On 5726, I really wondered so I called the watchmaker in PP service center I know, he said the annual calendar module on both watches are quite similar. And there s the date that we cant start to set up on (I cant remember), otherwise the month ring wont move at the end of the month. After setting up the new date by his recommendation, my 5726 works fine. No need to open the case at all.