I created a terms and agreement GUI and I wanted it to show up after 5-10 seconds after a player (or me) joins. I took a wild guess while attempting to make it work, but it didn't. Here's my wild wild guess:
while true do
script.Parent.Parent.Visible = false
wait(12)
script.Parent.Parent.Visible = true
end
Apparently, the local script is inside the Frame of the ScreenGUI.

5 comments
So apparently, this pops up when I tested my place with your suggestion: 03:54:51.416 - Something unexpectedly tried to set the parent of Rules and Terms to NULL while trying to set the parent of Rules and Terms. Current parent is PlayerGui.
Is there anything else in the script? because my code isnt editing the parent of anything.
Well, this is all I've gotten inside this tree: http://prntscr.com/3yxb6z
i see 2 scripts
ShowGUIOnce makes the GUI not appear the second time you die and respawn. Delay is the script that is supposed to make the GUI show up, and I think that's where most of the problems are occuring.