I made a "tower" style cake (THe tetris from Dr. Who) .  It measured 12" high and 8.5" square. I constructed the layers as choc/vanilla and seperated them into three cakes with two supportive cake boards between choc/vanilla cake sets to help with cutting/serving and prevent shifting when being transported.  I placed a plastic dowel through the center of the entire cake.  I covered with IBC (crumb layer) and put the freezer.  I took it out and let it sit for two hours, put another layer of IBS and began making the fondant panels. I rolled out  fondant using the orange (medium) guides to cover the styrofoam top (which had a light inside) and it began to tear when I was smoothing it out.  I re-rolled it using the yellow (thicker) guide and was able to get the top covered.  I used the same guide for the side panels.  I let the panels sit under a fan to harden before putting them on the cake to make them easier to handle and make for smoother fit.  After I got the cake covered and was making the decorative strips for the corners, I began having trouble with the IBC seaping out the bottom and side seams.  I make sure there were no bulges or bubbles and thought it might be the weight of the fondant.  I supported the sides with boxes overnight and thought it was going to be ok because the cakes and IBC were at room temp.   When I delivered the cake, it was seriously slipping and the buttercream underneath was bulging.  The cake layers appeared to be settling and now the dowel was sticking up where it had not been before, so not the top was not sitting flush on top of the cake.  I cried all the way home.  The party was that night so there was no time to remake or try an extensive repair, but I was not sure what was causing the failure to even address a repair.   

I researched and did exactly what others had done and this cake was an embarassing failure.  I cried and swore I would not ever do fondant again...my poor husband.  He begged me not to change my recipe's that it was what people loved about my cakes but I cant build a business on fondant failures.  What am I doing wrong.  Three days earlier I did a plumbers butt cake and it was perfect.  Usign the same IBC frosting and fondant.  It was 6" tall and other than a tiny bit of IBC seaping out at the bottom, there were NO issues.  What am I doing wrong? Was it a construction failure?  Decorating Failure? both?  Someone please help me ....

ATry using modeling chocolate instead. Much easier to work with especially for panels. Or you can cut out your fondant panels and let them sit in the freezer for 20 minutes or so.

Rice crispy treats can be formed into any shape, I would have made the tower with crispy treats. I just made a small barn topper with rice crispy treats and it was so much easier than using cake. And then make a sheet cake with the tower stacked on top.

As for your IMBC, I use smbc and have never had oozing problems. Too warm perhaps?!

Don't give up. Making mistakes is the best way to learn.

Gourmet Whisk Dr Who runs around the universe in  a Tardis.  Just another Dr Who fan, nutcase here.  Tetris is a game.

Sorry that I can't help you with the cake.  I very rarely stack.

I don't know where you are located at, but could the weather have played a factor?  If you are in warmer climate or high humidity area your icings can soften to the point where they ooze because they are melting.  It also sounds to me like your fondant was a bit too soft.  Did you warm it up in the microwave perhaps?  I do that to make kneading a bit easier and then I allow it to sit a bit to dry allowing it to firm up again before applying to my cake.  Just asking.

Did you have a series of dowels within the tiers in addition to the center dowel?  The plumbers butt cake did have an issue if a bit of IBC was seeping out of the bottom.  I don't use IBC so don't know what the problem is though.

Haha, i was going to say the same thing! TARDIS- Time And Reletive Dimensions In Space. It's not Tetris. Tetris is an old videogame.