Created attachment 177919 [details]
Video of Reproduction

SUMMARY

Hovering over the Application Launcher icon, then an application icon, causes the tooltips to become strangely stretched. This does not happen when hovering over only application icons. 

STEPS TO REPRODUCE
1. Hover over the Application Launcher icon.
2. Move the mouse directly over an adjacent icon, then back over the Application Launcher icon.
3. Repeat until the issue occurs.

OBSERVED RESULT
See attachment

EXPECTED RESULT
It renders properly, as it appears when hovered initially.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20250130
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.10.0
Qt Version: 6.8.1
Kernel Version: 6.13.0-1-default (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 9800X3D 8-Core Processor
Memory: 46.6 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 4070 SUPER/PCIe/SSE2

Widget Settings:
General:
Show small window previews when hovering over tasks: Yes
Hide other windows when hovering over previews: Yes
Mark applications that play audio: Yes
Fill free space on panel: Yes
Use multi-column view: Never
Spacing between icons: Normal

Group: By program name
Clicking grouped task: Shows small window previews
Sort: Manually
Clicking active task: Minimizes the task: Yes
Middle-clicking any task: Opens a new window
Mouse wheel:
Cycles through tasks: No
Show only tasks:
From current screen: No
From current desktop: Yes
From current activity: Yes
That are minimized: No
When panel is hidden: Unhide when a window wants attention: Yes
New tasks appear: On the bottom

ADDITIONAL INFORMATION

If the icon belongs to an application which is currently open (and thus shows a preview when hovered), the issue still occurs but less frequently. If the application is closed (the application is pinned), the issue occurs nearly always. The tooltip for the Application Launcher is also stretched more frequently than the tooltip for the application.

I'm able to replicate this with fractional scaling enabled and disabled, on both my displays, with the task manager on both the right and bottom sides.

kscreen-doctor -o
Output: 1 DP-1
        enabled
        connected
        priority 2
        DisplayPort
        Modes:  1:2880x1800@100!  2:2880x1800@120*  3:2880x1800@50  4:2560x1600@120  5:2560x1600@60  6:2560x1440@120  7:2560x1440@60  8:1920x1200@120  9:1920x1200@60  10:1920x1080@120  11:1920x1080@60  12:1920x1080@60  13:1920x1080@50  14:1680x1050@60  15:1280x960@60  16:1280x720@120  17:1280x720@60  18:1280x720@60  19:1280x720@50  20:1024x768@60  21:800x600@60  22:720x480@60  23:640x480@60  24:640x480@60 
        Geometry: 636,1728 1800x1125
        Scale: 1.6
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: unknown
        HDR: disabled
        Wide Color Gamut: disabled
        ICC profile: none
        Color profile source: sRGB
        Brightness control: supported, set to 27%
Output: 2 DP-2
        enabled
        connected
        priority 1
        DisplayPort
        Modes:  25:3840x2160@160!  26:3840x2160@144*  27:3840x2160@120  28:3840x2160@60  29:3840x2160@60  30:3840x2160@50  31:3840x2160@30  32:2560x1440@144  33:2560x1440@144  34:2560x1440@120  35:2560x1440@99  36:2560x1440@60  37:1920x1080@144  38:1920x1080@120  39:1920x1080@60  40:1920x1080@50  41:1680x1050@120  42:1680x1050@60  43:1600x900@60  44:1280x1024@120  45:1280x1024@75  46:1280x1024@60  47:1440x900@120  48:1440x900@60  49:1280x720@60  50:1280x720@50  51:1024x768@75  52:1024x768@60  53:800x600@75  54:800x600@60  55:720x576@50  56:720x480@60  57:640x480@75  58:640x480@60  59:640x480@60 
        Geometry: 0,0 3072x1728
        Scale: 1.25
        Rotation: 1
        Overscan: 0
        Vrr: Automatic
        RgbRange: unknown
        HDR: disabled
        Wide Color Gamut: disabled
        ICC profile: none
        Color profile source: sRGB
        Brightness control: supported, set to 50%