Yes you can redo it...carefully cut/lift the fondant off the cake, then scrape off the buttercream...see if it looks like alot of the filling squeezed out. You can if needed carefully take top layer off and redo the filling, add some ps to your buttercream for a really thick buttercream and pipe that around the edge so the filling does not seep out again...then crumb coat again and refrigerate a while, then start over with fondant. Hope this helps...I remember a few times redoing a cake like 3 times, talk about frustrating...once in a while it can seem nothing goes right! Good luck!!