What's the most costly commitment your team has dropped in Slack?

What's the most costly commitment your team has dropped in Slack and did you know it was gone before the client did?

We built Orchestra after watching the same failure happen repeatedly: something gets said in a client channel, both people assume the other has it, and it surfaces weeks later when the client asks. No one dropped the ball intentionally. The ball just had no owner.

Have others felt this and did you catch it internally first or hear about it from your client?