I still think Blabla2 means the same, if I read his French correctly. If the polycount on an object is high, it is heavy, and this burdens TG. Or the loaded maps (textures) are too large.
Peut-être, Blabla2, il faut changer les textures (tiff, jpg?) que l'object utilise. Un peut moins de pixels, 50%.... 20%...? (Sorry for my awful French).