To be fair, this happens at most airports on a regular basis. I just find it hard to understand that these types of errors are seldom noticed or corrected.
When I complained to Belfast International back in January that the departures page on their website was 'stuck' ( same data repeated for two or three days ) I was told that the person who updates the flight information was off.
So for some reason some Joe has to sit and type-in data ( or at least press a 'publish' button ), hence I assume the drop in accuracy in evenings and weekends.
I agree entirely with you; for many passengers and those collecting them from airports, the flight information boards are the only source of data since airport and airline staff are uncommunicative or know less than FR24. But that dependency is not reflected through the provision of accurate information.