They were running on a pi3b±Stretch, with (I think, no longer have it) PyMC 3.7, Numpy 1.17, Theano 1.0.4. Now trying on a new setup on pi4-Buster with PyMC 3.8, Numpy 1.18, Theano 1.0.4, and the pi3b+ is wiped/refreshed and is now running the updated linux Buster also, and new python, PyMC, Numpy & Theano.
As a little test, prior to replying here now, I have tried with all the combinations of (PyMC[3.6,3.7,3.8] ; Numpy[1.16,1.17,1.18], Theano[1.0.4]), printed version numbers align with the changing installations but all give the exact same error at precisely the same point in sample execution.
As they’re newly setup, it’s possible I’m missing some dependencies somewhere, but I’m not seeing any errors or warnings of such, obvs pip handles python dependencies, but could there be something on the compile side, flags or libraries, that are out of place?