While in a GUI screen that uses a slider at the right hand side, resizing the window using the cursor, switching between fullscreen and windowed mode with a keybind, double clicking at the top of the window to maximize it or double clicking at the top of the maximized window to restore it to its default size, resets the slider back to the top, no matter where it was.

Steps to reproduce:

• Launch Minecraft
• Click on "Options..."
• Click on "Controls..."
• Click on "Key Binds..."
• Scroll down (as much as you want)
• Do one of the following actions:

1. Press F11 to make the game fullscreen or windowed (depending on its current state)
2. If windowed and not maximized, resize the window using the cursor
3. Double click at the field where the title of the window is to maximize it or restore it to its default size(depending on its current state)
4. Use any size related option after right clicking at the field where the title of the window is

• Notice the GUI and the slider move to the top

Note:

You can reproduce this in any GUI screen that uses a slider. I used the key binds screen because it is longer than many others, which some players wouldn't be able to reproduce the bug on because of their GUI scale.