In Unity 2017.x, the behavior of curve editing was changed and this broke the visualizer in a way that is not easily fixable.
The work around is start your visualizer, select the asset you want to visualize, and then edit it in the Gaia Resources file instead of in the Visualizer. This will still have the effect of updating the visualizer in real time.
When you want to select another asset, go back to the visualiser, select it, and then go back to the resources file and edit as before.
This work around only applies to curve editing - everything else works as normal.
I will re-do the visualization system in Gaia 2.