I've been making cake for about 2 years now never had this happen...4 layered cake, leveled layers, buttercream dam with raspberry filling, buttercream frosting, decorated on top with macaroons and candy. Refrigerated overnight then kept indoors in AC till ready to serve. Cake was fine after removing from fridge for about 4 hours then suddenly was leaning tower! So much that I had to place a wedge under back of cake board. What went wrong??

It is my guess, @1haleyj ‍, that the warmer (than the refrigerator) air and humidity took a toll on the buttercream.  I know lots of people successfully leave buttercream at room temp, but I always seem to have issues if the cake is left at room temperature for more than a few hours.  I have had my hands slapped, but for fairly tall cakes, like your four layer, I use three or four straws or dowels, just to be safe from slipping.

I have made a three layer tres leche cake before and luckily it never toppled over!! I even had fruit in-between the layers and all cakes were soaked with the mixture of tres leche milks. It was a huge cake and very heavy with all that milk soaked into it. Everyone said it was better than the Latino bakery Tres Leche cakes. Probably because I had lots of fruit on top and in-between the layers.  We kept it in the refrigerator until we were ready for the cake!!! If it had been sitting out it may have toppled over so the refrigerator probably saved it from doing so. 

Thanks! 

BTW, your cake is cute!!! Sorry that you had such a bad time with your cake!! 

ms. sandra, absolutely nothing wrong with playing it safe and trusting your gut -- and this is exactly why you/we/i do add dowel sometimes -- even to one tier cakes --

and ms. haley, the raspberry filling might have been the culprit here -- sometimes i put a dot of icing in the middle of each layer before applying the filling all around that -- to add a little oomph to the strength of the dam -- for larger tiers you can make few wheel spokes

It is rather unusual for that to happen.  I agree w/the poster who mentioned it probably was hot, humid weather that caused your problem.  As I said in other threads I have worked mostly in hot dry places but did have a 2 yr stint in northern IN so do know a bit about working in such conditions.