Help, first attempt

Got a Granite Ware pressure canner, put in 4 x quart jars filled with beef. It comes up to steam and the 10 weight starts rocking about every 1-2 seconds for 5 mins then stops rocking. If I nudge the weight it starts rocking again but will then stop again. Read online that the weight only needs to rock 2-4 times a minute. The gas hob is on high, why does the weight stop rocking?