Gotcha, so basically a clean reinstall of their drivers.
Based on your initial description, it's not behavior I've been able to reproduce on my devices with any of my SpaceMice, though perhaps there are some Fusion settings we have set differently.
In general, when the concern is regarding a plane not moving as expected, I caution users to check the 3DxWare driver page for Fusion and toggle off the Sketch Lock and Lock Horizon options, as these are newer options with the latest SDK and are unexpected by longtime SpaceMouse users that update to newer drivers. You can also try toggling Fusion to use the legacy SDK under Fusion's Preferences > Compatibility and Troubleshooting > SpaceMouse driver, and see if this is a factor.
Also, please check what canvas camera view you are using when experiencing the behavior - some plane-locking functions only work while using Orthographic, or Perspective w/ Orthographic faces, and an unexpected switch between Ortho and Perspective could be a factor.
Lance Carocci
Fusion QA for UI Framework/Cloud Workflows, and fervent cat enthusiast