Straight edge bending when curve introduced on face

SketchUp
1

Having a bit of trouble with creating, say, a box, then I want to push/pull a curve I drew into face, but when the curve is drawn, it bends the edges. Is there any way to stop this, as it also changes the face into a heap of triangles.
Heres some pics to show whats happening.
The red circle is the next pic zoomed in, and the blue is all the triangles that sketchup changed the face into when the curve was drawn.

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Here it is zoomed in, you can see the straight edge should follow the red axis, but after I drew the curve (to push/pull), it warped the straight line. How do I stop this?

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2

I can’t tell eactly what you’ve got going on from your screenshots. Could you upload the SKP file?

3

How big is the object you are drawing? If edges are drawn closer than about 0.001 inch apart, SketchUp’s cleanup action may merge vertices and warp edges. If this is the situation the fix is to scale up while drawing and then back down when finished.

4

Scaling up x10 worked well, thanks.