Field rotation and libration are both reasons why you might think it's "shifting."


So taking a pic of the moon at a set time for a few years like taking a pic every august at 21:00 and comparing them would prove that field rotation and libration is the cause ?

Why would you think the moon would look the same at a given time of day on a given date each year? The moon's orbital period is 27.3 days... that doesn't divide evenly into the earth's 365.25 day orbital period around the sun.