Inverted Mesh leaving Gaps not filled

[banktoner (bluric_32bit)]

I was modeling my new model for my new game but when imported to roblox studio
suddenly realized there was one gaps not filled which appears to be bug

also showing that my model has odd negative scale so i inverted my mesh
tried with DoubleSided but nothing works
Every part is fine but not this one

Rendered in blender + shadows

i don’t know if it was really common since my permission to report this in #bug-reports are off since at the beginning

what makes it like this?

[ParallelMayhem]

Try selecting the problematic mesh in blender, go to edit mode, then the “Mesh” dropdown, and under “Normals” select “Recalculate Outside.” Now export it again and try importing it back into roblox studio. Let me know what your result is.