The Ripple Effect

Have you all ever experienced this ripple effect in your royal icing?  You know, the kind that goes on beautifully, you walk away for 20 minutes and come back to a wavy mess!  UGH!  Why......???

Let me just say up front that I do not know the sole reasons this happens.  I can tell you, however, this has happened to me on two different occasions and I believe for two very totally different reasons.  

Would you believe the cookies above were BAKED at the same time/same way AND iced with the SAME icing as these cookies below?

So really...what gives?  Why is one pan visual perfection and the other visual crap?  I cannot really say for sure, but I can tell you exactly what I did and my theory.

I'm a heavy icer and I like to lay it on thick.  I prefer a 20-second royal icing.  So with the circles, I laid it on like I always do and shook it side to side to even it out.  On the hexagons, I did the same thing, however, much slower and less even.  I didn't go in full circular even actions.  The icing did not shake out as easily.  The cookies were bigger, and I feel I simply did not move quick enough leaving lumps behind to dry before everything could settle in nicely.  The cookie was not under bake.  Utah has no moisture.  And like I mentioned, these hexagons were baked at same time/same thickness as the circles and iced with the exact same batch of icing.  So that is my theory for what it is worth.  If I were to go back and do it again, I would thin the icing a little bit and work to fill in the hexagon quicker to assure nothing dries before it levels out.