To start of, this is not top down design, where I start in an assy and make parts as I go. This is a straight up part made in its own. As in an assembly, if you select extrude the only option you have is to remove material. But while in a part file, extrude feature will add or remove depending on if I select the remove option.
Furthermore, it seems this problem does not even pertain to the specific part I originally inquired about. I created a new part making a 10 inch circle extruded out to 2 inches, then I made an 8 inch hole centered inside this circle. How this hole is created does not matter. I tried 3 methods, first I made one solid extrude of the 10 inch circle, then created a new 8 inch extrude with the remove option selected to create the hole. my second method, I created one extrude with two circles in the sketch, one 10 inches and the other 8 inches. My third method, I created one extrude of a 10 inch circle, then I created an 8 inch hole with the hole feature, again centered inside the 10 inch hole. All three of these methods gave me the same result with my slot that follows the outside profile of the 8 inch hole.
This problem seems to be specific to my dimension (also yes, I always use locked dimensions. I never leave a dimension available to be dragged out of sketch). When I create this slot that follows around the outside, it does not matter how deep the slot goes, I tried a shallow slot of only 0.050" deep to a full depth of 2" deep. This is the kicker, what seems to make the difference is the distance this slot is away from the inside hole. More specifically, if I have the distance as .1" offset, the hole is shown the next time I restart the program and open the part. But once I move the offset of the slot .099" restart the program and open the part voila, the graphics is messed up again and there is a surface showing where the hole should be.
I've uploaded some pictures of the part. I hope they are showing in the order I created and named them. The first (extrude1) should be the extrude in shading display style with the hole not visible. This is my issue, as anytime I have the part that has this slot around the outside edge this happens.
My second and third image (extrude2 & extrude 3) show why this is a graphics issue and not a physical part issue. The second image shows when I hover my mouse over the surface it shows the inside wall of the 8 inch diameter and does not highlight the surface that should not be there. The third image is in "no hidden" where you can see it shows as it should, although once I switch back to "shading with edges" this unwanted surface appears again.
My fourth image (extrude 4) is just to show my sketch of this part, this image is from my second method as mentioned above, where I just had two sketched circles and the following extrude makes a "tube".
My fifth image (extrude 5) shows the slot that is created. In this image I have the dimension set to 0.099" and from this dimension and lessor, this problem seems to be consistent. Again, once this dimension is 0.10", this graphical error does not seem to occur.
My sixth image (extrude 6) shows what the part should ultimately look like (in this scenario), you can slightly see the white background in the slot as this is where the slot follows all the way through.
hope this helps understanding my problem.
Edit: I've added three more pictures. They are of the modelcheck option from the File>Prepare>modelCHECK Regeneration. Here I get lost and have no clue as what this pertains to but thought maybe this could be similar to geometry check. The result of this modelCHECK does not change when I increase the slot offset above 0.10" though and gives me the same result.
