The usable automated task 'add user to local group' does not have any failure conditions,
so if it is returning an error it would still show up as successful in the dashboard with no indication that it failed whatsoever.
We contacted SolarWinds Support and this was their message:
"I downloaded the script and had a look and there does not look to be any failure conditions.
Currently there is no way to change that on the dashboard and is something that would need to be submitted as a feature request.
However what you could do is add the script (so that it downloads to your device) then edit the downloaded script yourself to add a failure condition.
Christopher Barber | Technical Support Representative, Associate | SolarWinds®️"
It is interesting though, that this has to be a feature request rather than a bug report.