Thank you for the support. I must say it's a hard nut to crack. To be more precise, when you import an obj file, you have to stop the script before you can re-export it. Studio does something when the script is stopped that validate the imported mesh. I haven't found how to reproduce it (and I tried a lot of thing). I'm constrained because the script acts within commands from VWD and it's not easy to change global behaviour.