The fare is not an "error", they've simply zero'd out all the fare buckets below M. You generally don't see accidental zeroing out of fare buckets, and in pretty much every case I have seen this is a preparation for dropping a route.
We just had a whole thread about this a few weeks ago
Alaska flight fares from SFO>LAS/LAX explode
Fares shot up to full fare on a bunch of routes. It was just temporary (an "error") and went back to normal shortly thereafter without any dropped routes.