Have you tried standing up? Depending on the size if you use 5-6+ perimeters they can be quite strong, assuming you have good adhesion. I don’t know what you are doing with the parts, material changes the characteristics a lot too.
It is odd I print round things often, standing and laying down, I rarely get flat spots. I just make certain the raft is deep enough to come up the sides.
I wonder just re reading all the posts if your printer need calibration? It is odd behaviour you are describing and I can’t reproduce it.