Created attachment 170606 [details] Screenshot SUMMARY When using the "Steampunk" theme, the panel is sometimes outlined when it floats STEPS TO REPRODUCE 1. Download and enable the "Steampunk" theme 2. Set the visibility of the panel to "Dodge Windows" 3. Use the system a bit OBSERVED RESULT The panel becomes surrounded by a dark rectangle EXPECTED RESULT The panel doesn't become surrounded by a dark rectangle SOFTWARE/OS VERSIONS Linux Plasma: KDE neon 6 KDE Plasma Version: 6.1.0 KDE Frameworks Version: 6.3.0 Qt Version: 6.7.0 ADDITIONAL INFORMATION Sometimes the border vanishes after a while
Since Steampunk is a third party theme, you would need to report this to its authors.
See also bug #488295, which is fixed in Frameworks 6.4.0