I work in a bakery where we take a 1/2 sheet cut it up into a 1/4 and the rest of that gets cut and stacked. These cakes always tilt on me and look like they are about to fall over and sometimes do.... any suggestions on how to prevent this from happening?
Is the cake levelled before it is stacked?
If you trim/level the top of the 1/2 sheet before cutting it into pieces that will help, I'm not sure if I'm reading your info correctly but if you are piecing together cut pieces of cake to make a layer in the cake then using some buttercream to "glue" them together would be helpful as well.
I recently worked in a local bakery and the cake layers were never level, as the shelves in the rotating oven were not level and it was a pain to have to level all of the cakes, full slab were the worst as one end would be 1 1/4" thick and the other would be 1/2" thick and unless the customer requested a filling they weren't torted and filled so you had to be careful not trim off too much so there would be some cake, we would have to use extra icing on the lower end to level it up.
I thought this said "Pervert" cake...
If the sheet cake is lower on one side than the other, cut it in half and flip it around so that the low side meets the high side and it evens itself out some.
When I worked at a bakery they would have us insert "wedges" of cake in between layers to make it level. At home I always level (trimming off the "hump" in the middle) my cakes but my homemade cakes seem to be taller than the sheet cakes at the bakery. The reason they had us use "wedges" is because if we leveled it there would not be much height left in the cake layer.