Getting Trixie to play nice

HI
I have just updated the hardware and the software running a 4-axis router to LCNC on Trixie. However, I am unable to stop the screen from going blank and, more annoyingly, when I run a program, the machine randomly stops moving partway through the job, and I have to press the stop button on the screen, click on the last line of code it ran, and then click 'run from here'.  When this happens, the screen is still active, but I am wondering if these two issues are related.
Can anybody offer a solution?
Thanks Everybody