A couple days ago, someone posted a bug report that a question that qualified for a Roomba automatic deletion criterion wasn't deleted despite qualifying for at least three weekly runs of the script that scans for it. Shortly after the bug report, on the next weekly run, it was deleted.
The author of the Roomba Forecaster user script, which displays whether a given question qualifies for a Roomba criterion, posted this comment, which reads in part:
However, in investigations/testing for Roomba Forecaster, there have periodically been questions which qualify under all published criteria, but which don't get deleted [...] However, the questions usually end up deleted by the Roomba shortly after I encounter them, even if they qualified for deletion for years, but were not deleted in that time. This implies either caching of some sort or something associated with just viewing the question.
Do the Roomba scripts not run on questions that aren't viewed in a long time? If not, what's the general cause of questions not being deleted despite meeting all criteria (including hidden ones)? Could it be that the script is non-deterministic just like badge scripts?