SUMMARY
Dropdown Menus and Boxes are drawn at incorrect positions when there is Fractional Scaling and Multiple monitors and different levels of scaling.
On a triple monitor system moving between monitors 1->3 going left to right:-
It renders fine on the first monitor. 
Now moving the Window to the second monitor, the moment the window is full inside the second screen all the dropdown boxes are rendered in the skewed point. It renders fine as long as a part of the window exists on the first monitor.
The Matter becomes worse when moving the window to the third monitor cause now the skewed point is further to the right and the dropdown box cannot be seen.


STEPS TO REPRODUCE
1. Set Kwin to use Wayland
2. Setup Dual/Triple Monitors
3. Set the Scaling factor to a value sub 100 preferably not divisible.
4. Open an application with a dropdown box.
5. Click on Dropdown box while the Window is place on each monitor

OBSERVED RESULT
The Dropdown Box renders in different positions not directly under the expected dropdown point
Moving further and further away everytime you move the window right

EXPECTED RESULT
The Dropdown Box should open directly below the Dropdown  button.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.24.5
(available in About System)
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.94.0
Qt Version: 5.15.4

ADDITIONAL INFORMATION