Was this issue ever resolved? I seem to be experiencing the same problem, but only on linux. I have two identical anaconda environments: one on my desktop running macOS, and the other on a linux box in a rack running ubuntu. If I sample with chains=2 and cores=1, everything runs fine on both machines. If I sample with chains=2 and cores=2, then running on the mac works fine while running on linux results in the sampling sitting at 0% indefinitely until I kill it. I’m not really sure how to begin diagnosing the issue as there is no error, and the python environments are identical as far as I can tell.