Steric trap
From apm
Not to confuse with kinetic traps.
In self assembly when the assembly process progresses in such a way that a prematurely added and non-leaving part by means of its shape, size, position, orientation, pose prevents the addition of further parts that would have been desired to be added.
Concrete example:
This can theoretically happen in brick type structural DNA nanotechnology if a void gets enclosed before it gets filled.