rstanarm stan_jm crash - Error in check_stanfit(stanfit)

Summary:

I was following the example in the rstanarm joint model vignette. I was at the very basic mod1 in the vignette and as I ran it, an error message pops out.

`SAMPLING FOR MODEL 'jm' NOW (CHAIN 1).

Chain 1: empty_nested() must be true before calling recover_memory()
[1] "Error in sampler$call_sampler(args_list[[i]]) : "
[2] " empty_nested() must be true before calling recover_memory()"

error occurred during calling the sampler; sampling not done
Error in check_stanfit(stanfit) :
Invalid stanfit object produced please report bug`

I then ran mod1 again and the following pops out:

Error in sampler$call_sampler(c(args, dotlist)) : empty_nested() must be true before calling recover_memory()

So it looks like I'm requested to file a bug report. Any help would be very much appreciated.

RStanARM Version:

The version of the rstanarm package I am running is 2.21.1

R Version:

The version of R you are running 3.6.2

Operating System:

My operating system is Mac OS X 10.15.5

Start by reproducing mod1 from the rstanarm joint model vignette with the reported RStanARM, R, and macOS versions. Trace the failure through sampler$call_sampler and check_stanfit(stanfit), then compare behavior with supported versions. Done means the cause of the empty_nested() error is established and the issue has a verified fix or compatibility explanation.