SUMMARY
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STEPS TO REPRODUCE
1.  make empty panel
2.  add icon-only task manager (configured to be 1 row)
3.  make the panel smallest size possible (while keeping it expandable)
4.  add 2 spacers

OBSERVED RESULT
things go weird as can be seen here https://youtu.be/xVJA4vk21WY

EXPECTED RESULT
for this to not happen?

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.24.4
KDE Plasma Version:  - 
KDE Frameworks Version:  - 
Qt Version:  - 

ADDITIONAL INFORMATION:
I installed arch via the archinstall and this is the first thing I wanted to do, i'd say this falls within the 15 minute bug initiative. this bug forces a person to force shutdown because nothing else is responsive (except the power button but shutting down has a stuck process so I had to hold down the power button. restarting works but I cant affect the panel or else i'd get stuck in the same loop, only removing the panel works.

Semi-related (1), the arrows affecting the maximum and minimum width of the panel are weird, both minimum arrows are pointing left and both maximum arrows are pointing right.
Minimum arrows should point outward of the panel and maximum arrows should point inward. 
So minimum ones like this "<------ PANEL ----->" and maximum ones are like the opposite.

Semi-related (2) the reason why I tried to use 2 spacers in the first place is that the icons-only task manager is not perfectly centered in the panel, its slightly to the left for example this is the normal panel in minimum size :
1. [----------] 
2. [--ICON--] < ----- this should be the behavior
3. [-ICON--] < ----- this is observed result.

I dont know if its related, but Latte dock does not exhibit this issue. and i'm back in windows atm but my linux installation is available if anything is needed.