Hi all. i need some help here. i got an old Gerber machine. still has original screw and rail. motor has upgrade to AC servo. Running Mach 3 now. machine is rigid, push gentry with no movement. now here is the problem. when i cut 2000mm, i get 2000mm sport on no problem. cut 800mm, get 799.70mm. 0.3mm off. cut 50mm. get 49mm, 1mm off. change step setting to make 50mm cut perfect. when cut 2000mm, gets 2008mm. i am confused. really dont know where to start. Please help. thanks (PS. this machine running fine before, all sizes cuts perfect. this is not a new build problem.)