Whenever I cover my cakes in fondant it ALWAYS tears in places when I put it on the cake. It's so frustrating!
Details: What fondant do you use? how do you roll it out? how do you transfer it to the cake? how do you attach it to the cake?
I use Dr Oetker Ready to Roll icing (I live in the UK) and I usually roll it out on a lightly dusted surface of icing sugar (I tried using shortening but it made it too greasy.). I coat my cakes in a layer of buttercream and usually transfer the fondant by hand.
Maybe the tearing is caused by you rolling it too thin? What do you cut the excess fondant with? I use a pizza cutter and havent had a problem yet, just cut close enough to the cake that I still have a little bit to 'push under' the cake at the bottom with the tip of the pizza cutter, sounds like you may be cutting too close which is resulting in the gap? I typically slide parchment paper around my cake to cover the board while im crumb coating it and dont remove the paper until i have covered in fondant. Now, i have never covered my board in fondant so if you are talking about leaving marks on that i have NO clue. Im pretty new to this so that may not be the best advice but its all i can think of.