A few years ago, I erroneously started a process on an unclean dataset, thinking it had been cleaned. This caused messages to be delivered to customers, asking them to take action, when in fact no action should have been taken on their part.

The cause? In a status update, the person cleaning the dataset said that she was "ready to begin". I interpreted that as "the processing process is ready to begin", not "the cleaning process is ready to begin".

When stakes are high, clear communication helps us all - even when whatever's happening is an SOP that you run every day.