these bug is difficult to reproduce. When I work with an assembly at some point it is not possible to select a part, instead a part behind or below this part will be selected instead. E.g. see the following pictures, I always tried to select the part below the mouse cursor, but instead other parts were selected, as you can see from the yellow lines:
Even the tool tip doesn't show the correct part.
Click Home/Reset doesn't help - one needs to close eDrawingsViewer 2015 and open the model again.
I tried to find a way to reproduce this bug, but this bug just occurs after some time you work with eDV 2015.