Convert closed spline to poly object does not create faces.

[miauuuu]

Here is a max2017 scene: https://drive.google.com/file/d/1ujWklf4yMLw3nrtTlzvxuI5bmLAcCVXI/view?usp=sharing

The problem is with the red shape. When I add Edit Poly modifier to it, or I convert it to Editable Poly there is no face created. Only 4 vertices, but no face.

Reversing the spline does  not solve the issue. Setting one of the other knots as first does not solve the issue. ResetXform does not solve the issue.

The blue shape has 4 splines. When Edit Poly modifier is applied to it only 3 faces are created. One of the splines has only vertices, but no face.

Here is an image showing the shapes and what is happening when an Edit Poly modifier is applied. Red and blue shapes are separate objects.

 

Does anyone have an idea why this is happening and how the problem can be solved?

[domo.spaji · Accepted solution]

That can happen if vertices don't lie on same plane...

Can!

[miauuuu]

You are right. Thank you.

Three of the verts have y coordiantes = 0,0 , the fourth vert is at 0.002. When I set one of the neighbors' verts of this fourth vert to the same Y coordinates - the face is created. If I set the fourth vert to y = 0,0 - the face is created.