Here's the problem illustrated by two very simple shapes....a cylinder and a hexagonal box. The hexagonal box is tilted slightly so to form angled top and bottom surfaces.
The profile is set to have 2 perimeters and 5 solid top and bottom layers. This is to give an even thickness to the external shell of the shape. I've omitted infill to ensure the various parts of the "shell" can be easily seen.
Here's a slice from v4.0.1...with the preview cut so to show the layers :
Notice that the top and bottom infill solid layers form a shell of similar thickness to the two perimeter shells....a nicely formed and quite rigid shape where the top and bottom sloping surfaces will print nicely! That is with the infill put back in!
Now here's the same slice from v4.1.0:
The cylinder is probably okay, but there are two points at both the top and bottom where the "shell" is a tad thin! The hexagon, on the other hand, has a very weak bottom facing surface,,,,and the top virtually as bad. I would expect this print to have a ridged finish on the top surface...that is if it doesn't fail altogether.
This..in essence....is what I am reporting as a broken feature in S3D....both solid top and solid bottom layers.
Attached is the factory file....use Process1 to slice.