Most easily reproducible with recipebrowser (quick) but also visible with simplebrowser (widget) on various sites (including qt.io). See attached screenshots. Resizing the window helps to reproduce.

--disable-gpu-compositing or enabling software rendering works fine. 5.15 works fine. Debug build works fine, only reproducible in release. No error message in console (apart from Vulkan disabled or failed to initialize).

I could only reproduce this on Windows 11 with Nvidia driver. Windows 10 with Intel works just fine.

The OpenGL context log is:

GLImplementation: desktop
Surface Type: OpenGL
Surface Profile: CompatibilityProfile
Surface Version: 4.6
Using Default SG Backend: yes
Using Software Dynamic GL: no
Using Angle: no