INSPIRED FUN - SEARCH BELOW FOR YOUR SUBJECT — royal icing fail

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? ...