Hm, maybe you're right, it really looks like 3dsmax wtf™ stuff. If i open scene that contains CoronaCamMod with spherical mode enabled in a brand new max session, spherical VR is off. However, if i create camera add CoronaCamMod enable spherical VR and then open aforementioned scene - VR is enabled here.
New daily with fixed installer, go try it out!
Does the object with grass material have thickness? Does it also happen if you switch UHD Cache to "animation" preset?
Can you send this object to support? https://coronarenderer.freshdesk.com/support/tickets/new