According to Wikipedia, the Seanad Éireann has only twice rejected a bill only to be overridden by the Dáil.
The first case concerned electoral reform which it's easy to imagine might divide houses.
The second, though, was the Pawnbrokers Act 1964. Skimming the legislation it seems to be as you would expect, various requirements for the licencing and record-keeping when operating a pawnbrokers.
What moved the Seanad and Dáil to come to loggerheads on this issue?