It’s funny I never had this problem when working at a local cakery. Now that I’m doing this myself from home though, it happens all the time. A trick I learned from other cakers is once your cake is together & pre-iced, lay a piece of wax paper across the top, then set the same size cake pan on top & fill about halfway full with water. I let this sit a minimum of 4 hours, then remove it, frost the cake &/or add fondant- ta da! No bulges! This just gives the settling process a little extra help. Be sure to give yourself plenty of time though! Also, idk where you live, but in humid areas, you want to be careful putting your cakes in the fridge, or leaving them in there too long for sure, or else you might end up w/sweating when you take them out. Good luck! :-)
