We're still on Octane 4.03 for C4D R19, Mac OS, but yes, I can confirm that in my experience, it will crash with more than ten Sub Material inputs to a Blend Material. Type 11 into the "Number of Materials" field of a Blend Material node, hit enter, and instant crash, even with an otherwise completely empty scene.
Fortunately for us, it just takes down C4D, not the whole system. In our case, it was easy enough to restructure the shader to work with those limits, and we rarely go anywhere close to ten Subs.
Technical Director - C4D, Maya, AE, - Washington DC