using 2016 , latest SP. I have noticed a persistent and irritating issue when using smart dimension. You select the tool and SolidWorks just sits for a few seconds before you can select entities to dimension. Very repeatable here in that it happens in drawings and sketches all the time regardless of model size. It reminds me of a bug we had in an early beta of SW2010 I think related to selection...there was this few seconds delay when SolidWorks didn't respond.