Mostly getting error fares is a matter of pure luck.
Around here, more often than not, they are posted in the Mileage Run forum - when they occur, but it isn't like they are a constant or even a regular thing.

Good luck and welcome to FT -- and please be sure to familiarize yourself with the different sections in the community -- SPAM isn't the most optimal spot for this query and that makes some folks around here a bit grumpy.