I do not agree with that the events are the cause of bugs. The event system is the perfect retirement of AL and for STS. It's my main reason to believe AL won't get another cap raise. It keeps the game somewhat interesting, without lots of work to create new maps, gear, maps, bosses, etc. The event system is the solution where the other legend games lack of. They truly died with the stop of development. It's been almost a year [march 2014] without a new level cap for AL and yet a massive amount players play the game, because they keep entertained with the events. Especially the events are well played and undeniable good for platinum sales too.
The last cap, STS had a race-to-cap contest with a big prize. This was fun for players, but the knife cuts both ways. It gave players an extra interest to cap their characters, but it also left them with nothing to play for faster than normal.

The first 'test' event and the elondrian event didn't had serious issues. Sure it had complaints, but bugs? Prizes have been adjusted over the events while STS learned from the previous events.
The lag issues started with the last introduction of the new client which was just before the halloween event. I don't know which changes have been made in the last client, but it seem to have a big effect. Bugs might be part of the new client, it also might have been bad planning of the last 2 events (halloween & winter) colliding with the mayor lag-issue which had to be fixed like written in the OP.

If only other legend games had an event system...