Some Linux configurations may experience jitter of the editor window due to scroll bar functionality. There are a couple of things you can try:

1. Check your system settings for scroll bar behavior. Scroll bars that dynamically appear/disappear may contribute to the problem, depending on how they're implemented.
2. Try starting Fade In with the --no-overlay-scroll command-line switch, either directly from the command line or by adding it to Fade In's startup options in your launcher.
3. Try disabling scroll bars using Preferences > User Interface > Show scroll bars.