OS: Windows 10 pro 1803
Software: 3ds max 2019.1.1
ProRender version: 2.3.371(core 1.312)
Issue: Max crashes when connecting 2 materials in the RPR blend node from the material editor in a new empty scene.
(See screenshot attached)
Taught of using the RPR blend material to mix a RPR uber material or RPR PBR material like the standard blend material of 3ds max.
Now I see that this is not the purpose of the material node.
Still needs a fix to prevent users from plugging them in and crashing. 
I used the map blend instead.