I have a problem in ArcMap 10.3 that has been vexing me for years now, and finally figured out what the actual problem is. When in edit mode, I can neither snap nor trace to features in either the left 2” or the right 2” of the map window (doesn’t matter if I’m in Data View or Layout View). I can trace and snap anywhere else on the map window without problem – it’s just within the 2” to either side of the map window edges. If I pan or zoom so the features I’m working on are between those 2” ‘dead zones’, I have no problems. As soon as I move the cursor into those 2” zones, snapping and tracing stop.