For the ‘too many parameters to plot’ case, I wrote a function https://global.discourse-cdn.com/standard14/uploads/mc_stan/original/1X/b7864f42254fe1d3de1597ade2573009a6137526.R to try and identify problematic parameters. Limited testing suggested it was doing a reasonable job, you can find some further discussion in this post: Concentration of divergences
edit: If I’ve made any updates to the function, you’ll find it in the ctsem github repository…