I just did a 4 tier wedding cake covered in buttercream. it was 12, 10, 8, 6. Very little decoration, just ribbon around cake and silver initials on top. Each layer had thick cardboard rods, but in stacking, everything was straight until I put the 6 inch on top, and it was slightly off. I took it off, added a bit more icing, and it was better. I just delivered, set up and left. According to the customer, the cake toppled 2 hrs later. Since I was not there, I have no way of knowing how it happened. The customer is now demanding a refund. My questions are one, what do I do about this customer, and two, how do I better handle my layers being more even.