As @gewubs said, calibration has nothing to do with cutting ability.
Two suggestions:
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Making certain that the material tray is perfectly flat and level – no debris in the dimples underneath and the tray is seated in all four dimples.
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Making certain that the material itself is flat. My experience is that there’s “flat” then there’s FLAT . A very common gotcha is that even a visually undetectable warping of the material can cause issues out at the corners. If you tap on your material and hear a click or an hollow sound, it’s not FLAT .
Your best bet is to cut out a dozen or so Honeycomb Bed Holddown Pins and use them to make absolutely sure your material is firmly secured. I cut out a few from draftboard scraps leftover from various jobs – you cannot have too many of these. 
My cutting success skyrocketed when I adopted these as part of my workflow.
Best of luck!