SUMMARY

There is an issue with screen edge functionality on a multi-screen setup. Please see additional information below.

When a window is maximized and the dock is hidden, the dock won't show up when I move the mouse at the left edge of the left screen. 

STEPS TO REPRODUCE
1. Have a multi-screen setup
2. Add docks to the left and right edges of the screens
3. Maximize a window and move the mouse towards the edge of the left screen.

OBSERVED RESULT

When moving the mouse slowly at the edge of the left screen the dock shows up at 1px before the actual edge, moving the mouse to the actual edge it hides it again. When the mouse is moved in normal speed it does not show up at all.

EXPECTED RESULT

The dock should show up when touching the edge of the screen.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Arch Linux - kernel 5.10.8-arch1-1
(available in About System)
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.78.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION

The setup:

I have 3 monitors:
- left monitor at 90%
- centre monitor at 0%
- right monitor at 270%

I have 2 docks:
- at the left side of the left monitor (problematic)
- at the right side of the right monitor (works fine)

What I've tried:
- Tested all other edges, top, right, bottom, they all work fine.
- Toggled the "Activate KWin edge after hiding". There was no change.