I failed to admit in the previous post that I was fitting the radial velocity data with pure sinusoids, not proper planet-induced radial velocity models. I switched to proper models today, after taking a short refresher on the mean anomaly, eccentric anomaly, and true anomaly. I wrote (not completely) stupid python code to do all these things and got my MCMC running again. So far, it looks like it might work. Of course I am reinventing the wheel here.