I have gotten these on just about every cake I have covered. I have been using Marshmallow Fondant. This most recent is Michelle Foster's Fondant.
Is my fondant too dry? Too thick? I roll out the size needed plus a bit, and I do elevate the cake on a smaller pan to get the edges.
All advice welcome!
When I have had cracks, it's been because the cake wasn't properly supported. So what happens is the weight of the top tier pushes into the cake underneath, which causes the fondant to crack.
I have no idea if that's what is causing your problem - just thought I'd would share one of my experiences.
The only time I remember having cracking problems with MMF is when I overnuked my marshmallows. Like the previous post - no idea why it's doing that but I also never elevate the cake - if you go on youtube and view a tutuorial (sorting by ratings is always good) they'll show you how to fuss with it so that elevating is not necessary - hope this helps