I have had this happen only a few times and I don't understand why or if I'm doing something wrong to make it happen. On the side of my cake the icing gets an air bubble about the size of your thumb, it actually pulls away from the cake, sometimes I can take a straight pin get the air out and push it back. Does anyone have any idea as to why it's doing that? Help please

This just happened to me this weekend! I kept having to push the icing back onto the cake. I was just hoping none of my guests saw it.

fermentation? possibly.

Was the cake cold when you iced it? This ONLY happens to me if I fridge my cakes and ice with American buttercream. And it only happens to me in the summer when it's really hot.

I think it has something to do with the condensation of the cake causing the icing to separate.

I don't really use American buttercream that much anymore, but when I do, I don't refrigerate it before icing it.