Im trying to edit a part in an assembly, section view is on if that makes any difference. I am unable to select a dimension to delete or move it, I can only change the value. Dynamic highlighting is on. I have never experienced this before, only noticed it recently. I havent updated since installing on this machine so that shouldn't have anything to do with it. If i open the part and edit the sketch, no problem at all I can select it all day long.

Im on 2016 SP0.1

This is really starting to drive me mad, any ideas?