Various hard to track / repeat crashes on different machines with stanheaders 2.26.26/27

I am seeing issues on different pc's, operating systems, and software packages, ranging from complete freezing to weird errors compiling to rstudio sessions crashing, using R 4.2 / 4.3 . Specifically, software packages bigIRT and ctsem, which both use rstan for computing the log probability / gradient of fairly large stan models, and sometimes use the sampling procedure. Sorry for the terribly vague report I am trying to track the occurrences to make sense of them and trying to make sense of users reports, but I wanted to post something about it -- is there some awareness of the issues, are others facing similar problems?
As best as I can tell the problems started with 2.26.26 , but maybe some were there already with .25 I can't be sure.

Sometimes the issues only happen after analyzing data for a day, in other cases the crash is repeatable (for the specific machine / os / R version configuration) and happens quickly.

Start by reviewing the reports involving rstan, stanheaders 2.26.26/27, R 4.2/4.3, and the bigIRT and ctsem packages. Compare the machine, operating-system, package, and analysis conditions for freezes, compilation errors, and RStudio crashes. Done means a reproducible configuration or a narrowed set of conditions that explains the failures.