Flipped normals when i mirror a block

Hi @wim sorry I don’t have a picture for it, but I realize I didn’t explain properly what was happening. As the datasmith export to Twinmotion puts the gumball in the middle of the exported mesh (the tree block), we have created a small flat disc inside the tree blocks acting as a placeholder for substituting the trees for the hight quality trees in Twinmotion.
Those trees are included inside the larger blocks (villas) and those are sometimes mirrored. The small flat disc inside those trees>mirrored villas, appear to have the normal fliped and therefore once substituted in Twinmotion, places the trees upside down