My game is jittery, running slow, or has unstable FPS.
If your monitor's refresh rate is higher than 60 FPS, it cause unstable FPS issue for the game. Go to the Settings > Stablize FPS > On, which should help with this issue.
If you are on a device with multiple GPUs (such as laptops), make sure that the your device selected the right GPU to launch the game. Here's an article that may assist you.