While I can't answer this directly, I can tell you that I've had more problems with CBS shows on Xfinity streaming (and NCIS is a CBS show) than any other network. My best advise is when you have a problem like this go right to the CBS website and watch from there, I can tell you from experience that I never have problems watching any CBS show from the network site versus the Xfinity site which is so glitchy and bug ridden it's not funny.
- Norm