I know when I got one bow I thought there was a crack because of the same thing you mentioned about the two camo patterns merging- its a Hoyt with the forest floor camo and there are small lines running thruout the pattern that look in some places like cracks.Anyway I read somewhere that you can take a cotton ball and run it over the suppected crack several times and if it is a crack the fibers will catch... just an idea, but you still might want to take it to a shop.
Hope it isnt.....