you’re gonna have to show more than just the inside. Is there any parts on the outside?
sometimes roblox has some buggy artifacting so dont stress it that much.
theres something about turning off global shadows and turning on cast shadows in some lighting thread somewhere but i cant remember it.
you’re probably gonna have to change your lightingtype in lighting tab, shadowmap to future / voxel. it changes how shadows are rendered, unless youre not really bothered by that