How to re-produce it?
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open the PC and log in.
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plug in a extra screen via HDMI (The screen works well still now).
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Log out.
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Log in.
Then the mouse can move but not click anything. The clock in the top centre will still tick which shows Gnome still work not stuck.
More info
I have install Nvidia driver, and use Wayland session. I can reproduce the bug consistently.