For us to learn from what happened, tell us what happened. That's all.

Knowledge management gets people to share their know-how with others, to help them learn for the future.  Such learning can be positive - as in, "I found this worked really well, you should consider that approach as well."  It can also be negative - as in, "We simply got it wrong and you need to do something different next time round."
In either case, to learn from what happened, we need to know what happened.
Not what we want others to think happened.
Nor that which will paint us in the best light.
Nor that which protects our feelings.
Nor that which protects the feelings of others.
Nor that which we think may help us get promoted.
Nor that which will save us from embarrassment.
Nor that which may get us a pay-rise.
To learn from what happened, we need to know what happened.
That is all.

Such honesty requires and enables a learning culture and is facilitated by supportive and self-critical leadership.  For more thoughts and information on this and other issues, visit the free resources page on the Knoco website and download the paper on organisational learning culture.