I just started to have this problem. Before this everything was printing correctly.
Here is what I did so far on my Moai 130 and still got the same saggy print:
-tested the laser circle
-changed the laser from 58 to 60
-Adjusted the z reset pos 2 numbers up and down
-tried the gray and hi temp peoploly resin
PLEASE CLICK ON THE IMAGE TO SEE THE PROBLEM