This happens consistently and seems to be either a reduction in Roblox’s VRAM cap or its hardware throttling limit not respecting the VRAM cap. Either way, Roblox NEED to have better settings for the player and need to meet the industry standard for graphics settings, such as allowing players to control the VRAM cap, force texture quality and render distance, etc., Rather than a single very obscure graphics level which isn’t even respected most of the game (ie this bug).
This occurs moreso on experiences with more visual instances (parts, meshes) or when I have other programs using VRAM (yet my GPU still has more than enough spare VRAM) such as Roblox Studio. I have no performance issues and I have plenty of hardware being unutilised, and my system also has a very cool temperature under heavy load (low 80C) so there is definitely no thermothrottling occuring.