Stuttering when another window is open

I think this is better described as a video: https://youtu.be/bDFsksynmKk The video is actually recorded with KWin's Magic Lamp effect, buat Yet Another Magic Lamp also suffers from the same issue. tl;dr:

standalone window -> effect is smooth
another window behind -> effect is stuttering

Additional info:

CPU/GPU: i7-7700HQ/Intel UHD 620
KWin MaxFPS: 144

Compositor:

Scale method: Crisp
Rendering backend: OpenGL 3.1
Vsync: auto
Allow application to block compositing: ✓

Other enabled desktop effects:

Accessibility: Zoom
Appearance: Background contrast, Blur, Desaturate Unresponsive Applications, Fading Popups, Full Screen, Login, Logout, Maximize, Morphing popups, Screen Edge, Sheet, Sliding popups, Translucency, Wobbly Windows
Focus: Dialog Parent, Dim Inactive, Dim Screen for Administrator Mode, Slide Back
Show Desktop Animation: Window Aperture
Virtual Desktop Switching Animation: Desktop Cube Animation
Window Management: Desktop Cube, Present Windows, Resize Window
Window Open/Close Animation: Glide

zzag / kwin-effects-yet-another-magic-lamp

Stuttering when another window is open #33