There is a short writeup at http://mc-stan.org/misc/warnings.html#bfmi-low about what it means when BFMI is low, but I am at a loss as to what to do about it. One of the suggestions given is “reparameterize your model,” but what sort of reparameterization helps here? Also… I tried to read the refer…

Fixing "BFMI was low" problems

betanalpha December 21, 2022, 9:49pm 12

Probably not. See for example some of the discussion in Low EBFMI examples - #5 by betanalpha.

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EBFMI (very) low, looking for reparameterization advice Modeling fitting-issues , specification , cmdstanpy	27	1432	October 1, 2021
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