I’ve had this happen occasionally when working on the lobby in Mashables. It cannot be selected or manipulated in any way, and disappears if the place is reloaded.
This happens to me whenever my laptop sleeps then wakes up with Studio open. The rogue polygons always have a point at 0,0,0, and can only be seen when you look at them from a certain angle.
Possibly related to this, but whenever my laptop triggers the rogue polygons, a few random decals get screwed up and fade to black depending on how far away from them you are.
One is your dedicated card (extra, high-performance one found in a lot of desktops), and the intel is your integrated gpu (default, low-performance one). Typically your computer will use the dedicated card, but ROBLOX had a bug at one point where it would use the integrated one instead – not sure whether that was fixed or if that’s happening here.
Under the View tab on the ribbon, click Render in the Stats tab all the way to the right. In the frame that pops up in the first section called Graphics, what does it say you have for video memory? If it’s 128 MB ROBLOX is using your integrated card, and if it’s 4096 (or around that), it’s using your dedicated card.