Outer perimeter different sizes (Monoprice Maker Ultimate/Wanhao Duplicator 6)

I'm printing this out of ABS:
https://www.thingiverse.com/thing:1664313

I'm using Simplify3D as my slicer.

Print temp: 225C
Bed temp: 100C
Infill: 50%

Any ideas on why this might be happening?

http://i.imgur.com/oAoTv72.jpg

My suggestion is to lower the bed temp below the glass transition point of ABS (100C), and turn up the fans a bit. It can be that you are slightly overextruding and the extra pressure makes the structure buckle.

Not only that, but you can see the bottom of the model has "elephants toes", where it is slowly spreading out over the heated bed.

Also if you have a tight calibration the bottom layer get's 'smushed'.
I usually do this deliberately, for things that need extra stick and file the lip off.

Abs comes into the category of 'things that need extra stick' :-)

The recommended temp for abs bed is 90c.