I own a 2000 model Pentalift scissor Lift. It works fine, when a single person is in the lift, but when 2 people of average weight are in the lift it will not go up properly. We haven’t exceeded the rated maximum capacity of the lift platform. It seems like it does not have enough power or hydraulic flow to raise the platform with the weight of 2 people for some unknown reason. I had a look and there is plenty of hydraulic oil in the reservoir. Could it be due to some faulty valve or something restricting the flow? Can anyone offer me some tips where to check?