I had the same problem when I first started shooting the bow. I determined it was not the bow, but me that was causing the problem.

As the weather gets colder, your wearing more clothing, and probably changing your form when you draw the bow due to the cold temperatures. One thing you can do is to practice in the cold temperatures while wearing your hunting clothes, pay close attention to your form.

I noticed that I tend to drop my drawing arm elbow when it gets cold, causes the arrow to hit in a different spot than when I shoot during warm temperatures. I keep this in mind during the winter, be sure to remember to get that elbow up.