I am somewhat new to medium format and don't get around to using my RZ67 II ..

Recently, as I was using the camera for a project, i've installed a new battery before i start shooting ,shot two rolls tri-x & hp5 , both came with 5 nice large negatives while the other frames were blank ? the two rolls were shot with 110 & RB 65mm

a frined sugested that i wans't advancing the dvancing the crank all the way down , again shot two rolls yesterday , just to make sure that i was advancing the lever to move the mirror back down .. developed and scanned , still getting 4 negatives in one roll and 5 on the second ?