I have experienced this behaviour.
Following your suggestions using KDE System Settings I have change GTK Styles to blubuntu, the KDE Widget style and Window Decoration to Oxygen.
After using qtconfig I have changed the style to Oxygen.
Now the enviroment seems to be stable.
I have also experienced that the environment become stable using the --sync parameter
I have experienced this behaviour.
Following your suggestions using KDE System Settings I have change GTK Styles to blubuntu, the KDE Widget style and Window Decoration to Oxygen.
After using qtconfig I have changed the style to Oxygen.
Now the enviroment seems to be stable.
I have also experienced that the environment become stable using the --sync parameter