Hello,
This is a weird bug that you’re experiencing… I’ll ask you some questions that can help Roblox engineers in case they see this post sooner or later:
- Is it possible to share the reproduction steps? What feature did you use to import this 3D asset? Do you have any Roblox Studio Beta Features enabled?
- When making the model in the 3D software app, which can be Blender, did you check for any duplicated vertices at the same position? If not, make sure to select everything by pressing A through Edit Mode; Press M and select the option “Merge by Distance”. It will remove redundant vertices of the topology.