I just installed Plasma 6 on my work PC (KDE Neon). My main monitor has 2 panels: top panel and a left panel. Both panels were set to fill width/height, and it was causing my top panel to freak out. And the desktop to lock up. My fix for now is to set the width to custom and disable floating. I adjusted the height of my left panel to custom as well. However, I also noticed it was overflowing to my second monitor. My second monitor have top and bottom panels so it didn’t experience that issue ...