Help:VE126

tag-name must not be zero.

The value for the tag must be a positive number.

For example, the config.txt file for a type track which included the container -

endcap-prev
{
  dont-scale-mesh-to-fit-length         0
  mesh-length                           0
  
  track-lod-tree
  {
    mesh                                "prev"
  }
}

would be flagged with the error

! VE126: 'mesh-length' must not be zero.

The fix is to change the value for the tag to a positive number: in this case, the length of the mesh.