We had a minor train wreck in the Night Before Christmas also. Afterwards, the director was having a conversation with the husband of one of the sopranos. (He was in the audience, as he's currently taking some time off from the group.) She was telling him that she didn't understand why some mistakes are still being made. I have some ideas why some mistakes are still being made. For example, there are some mistakes on the practice CDs, so people are just singing what they are used to hearing. More generally, the rehearsal CDs often aren't continuous. In other words, if there are sections where a part doesn't sing for a while, the director will skip it. Or if a part splits into a divisi, she'll go over both separately. In either case, you don't get the sense of flow of the music. We only rehearse once a week, and even then, we don't always sing each piece from start to finish, so in some cases, it isn't until performances when some people have sung a piece from start to finish. There is also the issue of people not watching the director that I mentioned earlier. It's improved somewhat over the past few performances, but I think we need to do better. Our holiday concert and last performance of the season will be tomorrow night.
Lest you think I'm being too critical, I'm not trying to be. I think the group is doing a good job in general. Perhaps we are experiencing some growing pains; trying to take the next step in our musical development. (We seem to be asked to do performances more often, so from the audience's perspective, we're improving.)