I had installed Rubytmix included in SU 2017, for TANE SP2.

Whatever you creiate from SU, it will be faulty, especially for light option. Clixk light option to off.
First I tried to create very simple box, no material no color and Trainz version is 4.3 or 4.5. It will be faulty: low mesh poly is high.

And I try to fill Trainz version with 3.5 and repeat process. CM import this box successfully without error.