I have a 4 long and skinny floors of a building as subtools. They’re 3 mil each.
I had to move them forward so that when I rotated them their ends did not clip.
Now when I switch to perspective mode they become inverted, the normals flip. I have tried flipping the normals back under display, but when back in ortho, they are inverted there.
What can I do?
Not sure why this should be happening though I think it must purely be a display issue and the normals are not being flipped. Instead of [actually] flipping the normals you could turn on Tool>Display Properties>Double so you don’t see the effect.
hey thanks for the help, that kind of worked, what I noticed is that when entering perspective mode the model is also upside down, and perspective is far away, when in perspective if I press frame the model totally disappears.
Are you using a background image? And how did you move the model forward?
thanks again for the help.
I am not using any images, I moved the model forward by clicking draw and move modes and moving my mouse down while not clicking the gizmo… or up I can’t remember which way goes forward. 
I’ve not been able to reproduce the flipping but it does become difficult to manipulate a very long object and perspective doesn’t always behave as expected. You might try reducing the Focal Angle (in the Draw palette) to see if that helps.