Was this ever resolved? I’d like to revive this discussion but the “Warning: 1 Chain Finished Unexpectedly” is a frequent problem that seems to be coming up in multiple contexts with newer versions of Cmdstan and CmdstanR. I have a model that ran successfully with good convergence properties on an older version of Cmdstan, but now after updating (I don’t even remember what version I was previously on), I’m getting this error all the time for models and data that NEVER had a problem. Searching the forum and Github, this issue comes up frequently and all of the discussions just stop with no resolution (see below). Debugging is a total PITA because objects are never stored in R if the “Warning …” message comes up so you cannot even use $output(chain_id) to examine the details of the problem.
Here are other examples (all with no responses or resolutions from DEV’s; btw, if you want people to stop using STAN, ignoring their problems is a way to make them do it, so congratulations) …