Bug 429571

SUMMARY
Hi, my KoolDE setup mimics ubuntu: top panel with global menu + left panel holding applications' list.
When I tile a window, either half-screen or quarter-screen, but touching a panel, window resizing by grabbing an edge or corner of such window, works very inconsistently. 

STEPS TO REPRODUCE
1. With your kde desktop set up with a left panel and a top panel, open a window, say Konsole
2. quarter-tile Konsole's window by moving it into either of the top corners of the screen
3. with the mouse pointer, grab its exposed vertical edge(the side in the horizontal center of the screen) and pull it horizontally to resize the window in width.

OBSERVED RESULT
the window edge does not move to resize the window, or if it does, you can only enlarge the window and not shrink it back: inconsistent behaviour.

EXPECTED RESULT
window resizing by grabbing window's edge should work, and do so both ways, enlarging and reducing window's area. In this 2 panels setup, if you quarter-tile in the bottom right corner of the screen, resizing works flawlessly, as expected.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 20.04
(available in About System)
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
kernel version 5.4.0-54-generic

ADDITIONAL INFORMATION
Looks similar to bug 348640, but behaviour is different, and we're 5 years later.