Ok so I did not find a official bug report for this and no staff has responded to the thread yet. (see link under)
Please see see this Answer Hub link
Basicly when adding the 3rd instance to a instanced static mesh component it everything crashes.
I am on 4.6.1
Thank you for bringing this to our attention. I don’t often get a chance to sift through the C++ section looking for bug reports any more. I have moved the other post that you linked to the Bug Reports section, and I will focus on that post since it has a great deal of information about this issue.
This Happends to meu on Blueprints too.
Im Constructing procedural Low Poly Trees…
First pass Add trunk (one Instance)
Second pass add roots, (one instance for each mesh, in my case 3)
IF I Add, more than 2 roots meshes, the BP crashes.
Hey you need to set Auto Weild to false.
So all instances don`t become a single ridged body.
See link over for more info.