SUMMARY
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The mouse pointer was stuck after drag and drop in Dolphin. For example, the left click of the mouse remains lock the pointer keep the transparent png of the thumbnail taken in dolphin before trying to drop it in another application (such as a messenger). The transparent image stay attached to the pointer as if still lock and no key combination on the laptop can unlock it. The left click affect the other applications, for example if i move the pointer on "minimize the window" of an application. The only solution to unlock it to reboot the computeur (and not only disconnection or sleep mode). 
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STEPS TO REPRODUCE
1. Open a messenger application  (for example in Firefox)
2. alt+tab and click on a png's thumbnail in Dolphin
3. alt+tab again
4. It's like the left click is stuck even after release
5. You can move the pointer but the left click remains lock 

OBSERVED RESULT
The left click is lock with the "transparent image" of the thumbnail or the tab attach to it.

EXPECTED RESULT
By releasing the tab or the thumbnail, it is supposed to drop the image in a messenger or to detach a tab from an application.

SOFTWARE/OS VERSIONS
Operating System: KDE neon Unstable Edition
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.94.0
Qt Version: 5.15.3
Graphics Plateform: Wayland