Machine not ready error

Hi everyone, i am using the winpc nc with USB on my d840 stepcraft. For the last 15 days I am trying to solve the problem that occurs after 30 minutes of running the machine. The horizontal lines appears on the desktop and the machine stops running with the error message the machine is not ready. It seems that maybe the connection jack on the motherboard is loose and maybe losing connection. Did anyone had this problem and do you know how to find what is the problem?