Okay, the story has progressed a little further. New bow that starts out shooting good and then goes bad is almost always caused by string creep. It means the string and cables have settled in to their final service lengths. Nothing to worry about because it's perfectly normal with most factory strings and cables. But it does need to be adjusted before it'll shoot right again.

So, take the bow to the shop and have them twist the string and cables to get them back to their original length. Then you will have to retune it. Afterwards it'll shoot fine for quite a long time before you have to mess with it again.