The only thing requires what I'd call a break-in period is the rigging (string and cables). The rest of the bow is good to go. I assume you have factory rigging on it. From past experience and posts (search) the rigging on Mathews and many others is hit-or-miss. They may settle in (creep) in about a hundred shots or so or they may creep for a long time, constantly changing. However, it's usually a gradual process and not likely to change that much day to day.

Probably what you are experiencing is just a different bow with a different feel that you're not quite consistent with yet.Make sure you don't grip the bow tightly as this can cause torque which changes the point of impact. Keep a real close eye on the draw length for string creep. Easiest way to do this is to mark the side of the cam between the limb tips. Then take measurements of the axle-to-axle length and brace height. Check these periodically to see if they change.

Best bet is, sooner or later, get a good set of aftermarket strings on the bow and things won't be apt to change much after about 50 shots.