Hello! I have a scissor lift which was bought from Pentalift in 2002. It's been working perfectly until last week. Last week when I tried to lift it with 3 people on it, it didn't go up entirely. We used to lift up to 6 people on it, but now it's not lifting more than 2 people. I think it may require a major service, but I am trying to diagnose the issue myself. I am not very experienced with hydraulics, but would like to find out more about it. Where should I start looking? Does the DIY check up require something that only experts can deal with? If then will skip it.