This is a very well known issue that is caused by insufficient adhesion. The corners curl up during printing.
You should increase the adhesion by:
cleaning the bed (I use water and soap, others use isopropyl alcohol)
correct nozzle to build plate distance (dragging paper method),
using a brim or so-called mouse ears in your design,
There are a few issues that could cause this. Roughness in your z-axis lead screw as pointed out by @TheLamestUsername is a leading contender I would say. I'd also extended that answer to include checking the belts for your X and Y axes as well as making sure that the rods the gantry slide on are smooth since the fault appears to be in about the same X-Y ...
A member of the public on Stack Exchange's forum gave me the answer:
"The problem is not the hole 'collapsing' in and of itself. The problem is the material.
Versatile Plastic is a layered powder fused together with a laser in multiple layers, so the unused power has to come out from the various holes in the model once printing is completed. However, ...