material shift


roland versa cammsp-300v
material 3m controltac vinyl
long print job 48" x 65"
it is printing in one shot so it is printing 2 parts
about half way through the material has shifted and i have to reset the sheet which in turn cancels the job
i am printing one section and then printing it the opposite way to get
the other half but is there a way to stop this or am i doing something wrong or can the sheet be reset with out canceling the job