I'm having a problem where [c_markov] is sometimes generating a value outside of the expected range, which is then not handled properly by the [route] object. 

Where I've deviated from the help file, and where the problem undoubtedly lies, is in randomly generating new lists of probabilities to feed into the system. 

I've attached a patch to demonstrate the issue. And I should probably mention that I do not really understand Markov chains.

Thanks!

Joe