Cinema 4D R18 Render Problems

Ever since installing R18, I’ve been experiencing intermittent dropped frames when rendering.  The renderer also sometimes stalls mid-render.  Is anyone else experiencing this?  Does anyone know how to track down the problem (perhaps some kind of render log)?  I’m running Mac OS 10.10.5 on a Mid 2010 machine with 12 3.33 GHz processors, 64 GB memory, and an NVDIA GeForce GTX 980 Ti 6144 MB graphics card.

Thanks!