Looks like cupping. The suction from the peel process can pull on the layers deforming them.
Here are Few things you can try.
Add a side hole or a few side holes to minimize cupping. This will allow resin & air to flow in and out of the part during the peel process taking the force of your printed layers. (you can always print plugs to close holes when all is done)
if you can’t have small holes in your part you will most likely have to print it on a raft.
With that said there are 2 ways to do this.
2.1) let preform orientate the part for you like your others in the picture. This will likely leave a small deformation on the first few layers of the part.
2.2) Or if you prefer keep it in the orientation like you would print directly on the build plate… but place a raft under it. This would stop cupping from occurring but will most likely give your part a not so flat bottom.
To correct this you could add material to the bottom of your part and machine it flat and to size when all is cured.
Just some thoughts.
I do a lot of prints directly on the build plate and cupping is the biggest draw back other then the compression messing with my over all height.
Hope this helps.