maybe it was the way you started it up. What i like to do is keep the hopper and mixing zone bone dry, use a tissue or something. inject just enough water to cover the rotor. sprinkle in the first few kilos then the rest of the bag. then start the pump. by keeping the sides etc as dry as possible you reduce the risk of gear sticking to sides and ensure the material flows into the mixing zone as it was designed to with no restrictions caused by wet gear sticking to sides. Its only the bottom 5 inches that gets wet
thats not the best way to do it lee. put the water in as you said and then gently open the hopper lever until the mixing shaft is covered and close it again. Only then do you turn the machine on. Once you see some mixed material exiting the outlet turn the machine back off, open the hopper lever again to fill the mixing zone and your ready to go.