3DConnexion grumbles continue

Finally had time to start using Rhino 6.
All good so far, except my brand-new SpaceMouse Pro is showing altered behaviour compared with the old/obsolete one.
I prefer to have the Lock Horizon option selected in the 3DConnexion settings. Incidentally, this setting is not respected unless you access it via the in-Rhino command SpaceMouse_PopUp_menu and select the Lock Horizon option there. No biggie.
The real problem is: when rotating the perspective view with the regular mouse or wacom pen, you get a predictable and even rotation around the world Z axis.
Using the Spacemouse however, if you are rotating the view in either direction and you tilt the mouse so the camera/POV passes through the XY plane, the direction of rotation reverses.
Furthermore, if the camera is resting on or near the XY plane the rotation freezes completely. This makes the Spacemouse unusable in many situations.
There is no setting that I can find that has any effect on this behaviour.
This was broken somewhere between R5 with a SpacePilot, and R6 with a Spacemouse Pro.
Any ideas, anyone?

PS: there is no rotation at all in R7 WIP…