I found a cause.
I use this GNOME Shell extension.
https://extensions.gnome.org//extension/4691/pip-on-top/
This problem is a bug from this extension.
I will report this bug to extension's developer.
Anyway, This Issue is not Ubuntu's bug.
Sorry and Thank you.
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You received this bug
This is a video when it clashed.
** Attachment added: "IMG_2298.mp4"
https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1982611/+attachment/5605491/+files/IMG_2298.mp4
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Desktop Bugs, which is subscribed to
** Attachment added: "prevboot.txt"
https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1982611/+attachment/5605490/+files/prevboot.txt
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This is a clash report's link.
https://errors.ubuntu.com/oops/112d520c-0ce5-11ed-96b0-fa163e993415
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Desktop Bugs, which is subscribed to gnome-shell in Ubuntu.
https://bugs.launchpad.net/bugs/1982611
Title:
GNOME Desktop
