Component
One family that was attempted for a group and rejected, with the estimator's own explanation.
The estimator's diagnostic string is the most informative failure record available, so it is carried rather than replaced by a generic message. Failure rates by family and group size are a reportable experimental result, not log noise.
Parameters
rv
the family that was attempted, or null when the estimator produced no parameters
message
the estimator's own explanation of the failure