Opto display communication problem

We are using snap pac lcx r series and running our process, we are facing the communication issue for pac display. The communication between the controller and the pac display pc is getting disconnected due to which we are loosing the trend and the data. We need to login again to continue the trend. i have tried changing the baud rate but its not working. We are using a multi core wire for communication is the loss of data is due to that or what? Can any one help me out?