AI been having a problem. The last two cakes I have made started sinking on the bottom. Each tier is 4" tall with 2-3 layers inbetween. I use a BC frosting in cake smoothing consistency and then wait till it crusts before covering with fondant. Once I cover it with fondant and finish decorating it looks great. I box it up and it's ready for delivery the next day. When I go to take it out of the box, i notice that the bottom tier has sank and the fondant has the ripple effect.

What did I do wrong? As mentioned above, each tier is 4" tall with 2-3 layers in between. I have a cake board under each tier and dowel rods in between too. I also compress the cake layers as I BC each layer and let it crust. The BC is smooth by the time I go to add the fondant. Should I be adding a smalled cake board in between the layers too? As in, every 2" add a cake board with dowel rods under it for support so it doesn't sink? I dont understand why the cake keeps sinking. please help....

AWhat kind of dowels are you using and how many? once you fill the layers, do you let it rest before actually icing it?