Ok. So I believe roblox actually does that on purpose so that you can more easily look around in first-person. You can fix this by doing the following:
Insert a ScreenGui into StarterGui. Name it “FirstPersonBugFix”
Insert a TextButton into the screen gui.
Change the text button’s background transparency to 1.
Change the text button’s text to nothing.
Change the text button’s interactable property to false.