Hello,
The pulling back did not happen in softbake but before it after a long
relaxation. I used a rectangle silicon substrate. Usually the SU-8 retreats most
from the four edges of the substrate but extends and covers the corners. The
shape of the final SU-8 looks like a puddle surrounded by four concave lines.
The flatness is not that bad for the SU-8 puddle.
Cheers