I have a flashlight and cutscene script that always works 100% of the time in the studio and editor. Whenever I publish my game and play it on a server it just doesn’t work with a 10% of working. It always has an infinite yield waiting for children.
That error implies you used the FindFirstChild method or similar to find an instance that doesn’t exist (at least with that name). If you could include a copy of the script throwing this error, it might make this easier to fix.