The minimize animation/magic lamp is drawn to the center of the screen instead of the task manager, this happens to about half of the windows. A given window always exhibits the same behaviour.
e.g. The kwrite window always minimizes correctly to the task manager while the firefox window is minimized to the center.

Reproducible: Sometimes

Steps to Reproduce:
Minimize a window

Actual Results:  
Minimize animation is drawn to the center of the desktop

Expected Results:  
Minimize animation is drawn to the task manager

Problem has been present since plasma 5.7.0, 5.6.x worked just fine.
Using NVIDIA 367.35 GTX 860M
Scale method: Smooth
Rendering backend: OpenGL 3.1