We have a small factory. One-tank method. We cook a light lager. I use the method of assimilation, assimilated and harvest yeast 20% by 80%. I get 15 mil.cell / ml at the begining of fermentation. Before the filtration, after all yeast removals, there were 8-14 mil.cell / ml. now this number is 20-28 mil.cell / ml. from this problems with filtration. What can cause similar problems and what can I do to fix this?