Problem of CFaceTextureCoords is not valid

There are “CFaceTextureCoords is not valid” problems when exporting from XML to skp.

The face is tessellated and the uv coordinates are set as shown as below. (Front UV). However, the UV on the texture is correct.

When i open the skp file and try to find out the UV coordinates of the face, the value of the coordinates become 0s.

After fixing the problems in Model Info → Statistics, it shows the correct UV as what I have inputted.

Is there anyone meet the same problem as mine? May I know why is this happening?

It would be helpful if you posted some files (the xml and skp file) and some code that creates the skp file.