M&W 4500 rd baler

First time here, just bought a older M&W 4500 string round baler. I know it will take some learning but first time using it I baled hay until the tractor started to bog down, 1 sensor light started to flicker but too late, took 4 hours to dig the hay out. So I started to clock myself about 5-6 mins and got decent bales. But the sensors are suppose to be new. Did notice sensors are different in lengths (flat thin paddle piece) 1 is longer than other,  #1437981 C (Mexico longer paddle 2 3/8") other sensor #1437981 (China "artsway" 1 7/8"). Also isn't the roll suppose to automatic roll out, I go back there and give a pull and out it comes? I am use to square bales, like I said new at it. Anyway to test sensors, multimeter check? Thanks 

M&W 4500 rd baler