I am running current revision of Rhino 6 (6.16.19190.7001, 7/9/2019), Octane 4.05, plugin 4.5.0.111 and material previews are not working/corrupt.
Also running Nvidia Driver 431.60
They will not regenerate correctly if I explicity update individual materials or auto update all of them.
I have attached a screenshot of the problem.
Thank you!