I am making a 3 tiers cake with two layers each. I have filled the cakes with pinapple filling. I can see the buttercream layer between my cakes. Am I doing some thing wrong? Do I need to put more buttercream around each cake?
Try using a wider and thicker dam, minimal pineapple filling, and let your tiers settle before icing them.
Try a search (here or another search engine) using the words:
Yup, it's so common there's a name for it.
Filling it and then letting it settle with a little weight on top of it will keep it from doing that.