It’s a very ugly and inconvenient clientside bug. When loading a game, even though Roblox stores mouse icons and menu assets locally, they take some time to load for some reason. Long enough so that it becomes a glaring issue for the first 20 to 30 or so seconds of joining a game.
This becomes particularly annoying if for instance you join a game that has its music too loud. To turn down the volume you need to open up the menu, access options, and then turn down the volume. But in order to do that, you have to wait for the menu to load in, as the buttons “pop in” one by one (very ugly), waiting for your mouse to appear or trying to use the button hover to determine your mouse location. (When you hover over it the button disappears for a second as well)
Then you have to navigate the options menu with no mouse if it has not popped in yet.
Or the more common issue; when you join a game and you want to close the window, but due to awkward offset mouse sensitivity and the fact that your mouse is invisible, it makes this a lot harder than it should be.
Please have the mouse icons and the menu buttons load instantly, I don’t see there being a reason for them popping in so late.