I am using the scientific Geant4-software on the Linux Open SuSE system Leap v15 together with KDE Plasma 5.12.6 or alternatively with GNOME 3.26. Geant4 is the toolkit for the Monte-Carlo-simulation of the passage of particles though matter, and is offered by CERN. Actually, i use the version GEANT4.10.04.p02. It contains a subsystem for 3-D-visualization of the computed particle trajectories that is based on Qt5. During installation of the Geant4-package, CMAKE attracts the needed Qt5-components from the underlying KDE-socket. That is, both KDE and the Geant4-application use the identical version 5.9.4 of Qt5 and the same Qt5-implementation.
The problem is, that, if Geant4 is running on KDE, it is not possible to generate rotations and shifts of the presented visualizations with the help of mouse movements, i.e. the dragging of visualized objects is delayed by up to 30 seconds or more. Surprisingly, the problem does not appear if i use GNOME as embedding OS. With GNOME, the mouse dragging for rotations and shifts is working perfectly. Moreover, also using Qt4 (implemented in older KDE Plasma versions) is ok.
Thus, apparently the problem is not caused by the Geant4-visualizer or by its interface to Qt5, but is rather located within a strange interface mixing between Qt5 and KDE, when the same Qt5-implementation is addressed simultaneously by Geant4 and other KDE-applications.

Are there any hints or workarounds available to solve this problem? Or is it possible to remove it via Qt5 admin-tools? Unfortunately, I have not found such a tool for the actual KDE-Plasma5 version.

I also have this problem. Did anyone find a solution?