Been working on this for several days.
I have been getting strange results when 3D SLA printing a box and lid, and discovered that it is caused by the lid faces not being flat when exported to .stl file.
I have read other posts that say that this may be caused by sketchup’s tolerance when snapping to points, however I was pretty careful when I redrew this so that there was no ambiguity regarding any nearby points, and it was constructed using guide lines & dimensions and pull.
This is actually a redraw, I started from scratch, and it seems there is just no way I can create flat surfaces.
Attached is the sketchup file and the exported stl file as well as a screenshot of the slicer that is not seeing any surface as flat.
I have also use the dimension tool to check dimensions and diagonal vertical and horizontal measurements are all identical, this should prove that these planes are in fact flat, but they are not.