I work at a small hometown bakery where we do birthday cakes and wedding cakes. In the past we have had problems with "air bubbles" on the sides of layer cakes, but it was very limited.
In the past few weeks it has got worse, it seems like almost half of our layer cakes are having "air bubbles" or "blows" I dont know why the problem has got worse and don't know what is causing it.
Last week I did a 2 layer 12" round one evening, I checked it first thing the next morning, it was fine. I checked it around 1pm as I was carrying it out the door and it had a small air bubble. I got a toothpick, poked a hole in it and pressed the air out. When I got to my destination only 15 min. away, a spot about 6" across and all the way from top to bottom had fallen off. 
This was for my best friend so I gently picked it up with a spatula and pressed to back to the cake (thank goodness it was in the back). She was very understanding. But why did it do it
We have had this happen on everything from an 8" double to a 20" double, every flavor icing,
Does this happen to anyone else or are we doing something wrong?
HELP !
I don't know where you're located, but I just had my first blow-out in over a year since changing icing recipes. I'm in Texas, where it's been raining cats and dogs for weeks. It's the only factor I can think of that's different. I don't know why high humidity would cause it, but it's all I can come up with at the moment.
In responce to what type cake and icing:
We use a cake mix, and on our small birthday cakes we ice them fresh (don't freeze them) and on our larger wedding cakes we freeze our layers, pull them out the day before and stack them, cover them with seran wrap to thaw, and ice the next day after completly thawed.
We use icing made in our shop (not pre-made). We have had this happen on basic white icing, buttercream, and chocolate.
This was a minor problem in the past but over the last few weeks it has been almost half our layer cakes. I only recall one time with fondant.
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