Hi I'm doing some in context routing inside a large assembly, and I'm repeatedly getting drag and drop failures on some of the parts I've designed and added into the routing library. The odd thing is, is that when i close my assembly and re- open it on occasion it works. But it is a large pain in the butt to have to close and re-open my assembly a hundred times before lunch. Now I think this is a SolidWorks glitch because when i try to just open the part itself from the routing library (right click, open) it will not open, and this is happening to more than one specific part  unfortunately. I recently upgraded to Solidworks 2015 SP4 from Solidworks 2015 SP3 so I'm not sure if that has anything to do with it. Any possible ideas as to what may be causing my problem would be greatly appreciated!