It's so annoying. They're so pretty. You've worked so hard... and CRACK! What a bummer!
I am not a scientist, nor do I play one on TV, but I can tell you that from my experience, the reason that cake pops crack is all about temperature. One of many temperatures.
Is your cake ball is too cold?
Did you use the freezer instead of the refrigerator to let the balls set? Chances are they're too cold. I take my cake balls out of the freezer after just 30 minutes and move them to the fridge so that they don't freeze.
Is your candy too hot?
You really want to heat the candy melts until they're just melted. If you allow them to get hot, lots of bad things happen. Not just cracked pops, but the candy can seize, and you'll have to throw it all away. (gasp!)
Did you add a melted candy decoration after the pop "set?"
If your decorating bottle or bag of candy is too hot, it can also crack the coating. I've had this problem a lot recently. It's annoying. You want it, again, to be just warm enough to melt.
And sometimes, I've found that cake pops just crack. So, you hide that one in the back of your display, or "donate" it to the cause... you know... your stomach.
Do you have other decorating problems you want help solving. Ask me in the comments section below. If I don't know, I will try to find out!!