When the launcher executing some functions, its window content will scale wrongly.
Such as: Starting game, changing accounts, changing tabs, etc..
And when resizing the window, the window will be bigger than before and can't be smaller anymore.
Also, the scale of the contents will be normal again.
Please uninstall the Launcher, delete minecraft folder (copy its content elsewhere before deletion) and then reinstall, restart your computer. Then please try to boot the Launcher.
If this is still an issue, please record a video of this happening and attach it to this report.
If you are on Mac (Mojave or later), you can use
Shift+Command+5to open a built-in app for recording your screen.In case you don't have a program to record videos, we recommend using the free recording software OBS.
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