When launching KDE Partition Manager, it opens a PolicyKit dialog window in which it asks user to enter password. But if user decides to close application he is unable to do it until he enters a correct password or use xkill.

STEPS TO REPRODUCE
1. Launch partitionmanager application
2. Several windows will appear: main window, a small window with scanning status, policy kit dialog window. 
3. Try to close window with password dialog or any other application windows or try to enter wrong password.

OBSERVED RESULT
When you close a policykit window, another one immediately appears. This happens infinite times, no matter how much times you have tried to close it.
When you enter wrong password trying to make it fail several times, it keeps asking it.
When you try to close other application windows, nothing happens, as they wait responce from policykit process.
Use ctrl + alt + esc shortcut to kill the policykit window and partition manager shows no devices and no partitions. (Looks like it remains broken even after relaunch: policy kit window does not appear for application until relogin).

EXPECTED RESULT
User should be able to refuse to launch application without entering password.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.21.5
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2
Graphics Platform: X11

ADDITIONAL INFORMATION
In Gparted, the interface of the application is not shown at all until you enter password in policykit window. As for me it looks more intuitive then several windows of Partition Manager even when they are greyed out.
In Gparted, if you enter wrong password three times, it will stop asking it and simply will not launch. I think the same should happen in Partition Manager.