I figured out why it was looking posterized sometimes. One of my captures inexplicably shifts left or right by 1 pixel once in awhile.

I'm just going to use the first capture because the difference between one capture and an average of all 3 seems to be rather negligible in this case. I'm sure it helps out in some situations but in this case it just adds layers of complication with no real benefit. Of course I'll play with it as an afterthought but I think it's better that the preservation is as original as possible anyway.