Same thing occurs with my meshes at 50% of time. I can’t report this bug due to my rank Member. The only solution, that may work - invert that wrong verticles, but roblox can ruin them too.
Does the double sided property in Roblox Studio fix the missing faces? That usually does it for me.
I understand it’s not optimal, but it is a quick solution that might work.
Edit:
The mesh itself has tons of topology and general vertex issues as to why the mesh looks the way it does in Roblox Studio. Here’s a video of me moving around some vertexes to show what I mean:
Edit 2:
I’ve fixed the vertex issues and got it working in studio.