I had the same bad luck when building my rat rack and Lowes did the same thing to me with the cuts. I went back and politely complained and the manager said the saw is for making wood small enough to fit in cars, not exact cuts because the machine is so abused. I told him that when someone comes there with exact measurements, they need to know these things. Manager was a nice guy and made sure the cuts were right for me.

I am just going to steal one of my dad's table saws to save the frustration.