Split surface not working

Hello there,
I am currently trying to split/trim a surface that I created with a patch - it’s a terrain resulting from a group of contour curves.
I frist tried to split the surface with a rectangle from the top view. Secondly, I tried with four longer lines that resulted from the extension of the rect’s edges, but just one of them managed to cut the surface. I also used the vertical extrusions of those lines as splitting objects, but no success again.
Could someone have a look and give me a feedback on this issue?

//if you wanna have a look at the file, you can find it here - Split not working.3dm - Google Drive

2021-04-05 20_05_04-
You have 2 problems: you are really far from origin and using centimeters to draw mountains.
Both of those will lead you into having rounding errors and making rhino failing most of its math.

I scaled everything by 0.01 (so like using meters instead of centimeters) and it was enough: split works as expected.

If you have more problems, consider moving your geometries near origin and/or scale even smaller.

Thanks man - I didn’t realize that!