Call Techno, I'm sure they will help. They have good documents for checking machine alignment etc. I have a 054 gantry machine which shares a lot of parts with the LC but I have a spindle not a PC router. You don't mention bit size, depth of cut, material etc. Do simple test cuts like the box test come out OK ?
I have 2 Techno LC machines. a 4896 and a 59120.
I am crazy about both of them, and have yet to have an issue.
For your problem, Maybe you could run a simple grid of 12" squares and circles and see how they look over the length of the table.
Just a thought.