My automation sent the wrong pickup times—should we switch it off?

At 9:12, a member of our book-swap group replied, ‘Yesterday you said four. Your email now says ten. Which is it?’ I opened the spreadsheet and realised I had sorted the pickup-time column without keeping the names beside the right times. My little email script had sent eighteen messages from the muddled rows. Six people had received the wrong slot.

I stopped further sends and contacted those six with the corrected times. One had already rearranged her morning. I had tested the script with two dummy names, both assigned the same time, so my test never showed the mistake that actually happened.

The other organiser says we should go back to writing each message by hand. Before this, that took us about forty minutes per swap. I built the automation because we were doing it after work, and I liked finally having a quicker routine. Now I feel embarrassed defending it when somebody else paid for my shortcut with her morning.

Would a preview that we check before sending be enough reason to try again, or should we shelve it until someone else understands the setup too? I want those forty minutes back, but I also want a member to know which message she can trust.