Thanks Roberto. Can you update them to the latest versions and retry please?
conda update pymc3 theano -c conda-forge
It should be 3.9.3 and 1.0.5 after upgrading.
Regarding priors, it’s very important to be careful about them when using a hierarchical model, for various reasons that would be too long to detail here. You can take a look these recommendations, and at Richard McElreath’s Statistical Rethinking book (PyMC3 port).
Spoiler alert: I’ll talk about choice of priors in my PyMCon talk 