What is "ground shift problems"?

I did that once, grounded a controller up stream of a 10A DC switch and everything else to the battery. Reset the controller...
The Good News was that it took a 1" piece of wire.. The Bad News was that I had to do it.
I moved a part a tenth and re-poured the ground plane to do it.
I didn't think the change was serious enough to run the DRC again..

Bob