So, you mentioned this is a Website issue - I work in IT.
"I once had a project where we were decommissioning an Old System, as part of the process, we did an Audit on the Old System - I delegated this task to one of the Juniors in my team - they presented me with the Data, I reviewed it and it looked good - I signed it off and then after some other tasks, we proceeded to Go Live.
Unfortunately, in the Audit, a particular customer segment was missing (it was partially handled in another system that only talked back to the system we were decommissioning) - and so when we went to Go Live - bad things happened, we had to roll back, I got some egg on my face (as I had signed off on it and I wasn't going to throw anyone under the bus) - we re-did the audit and addressed the issue and then re-attempted the Go Live at a later date.
The lessons to learn here are to take care when auditing data and in our case to double check all the active connections to that system were coming from where we thought they were coming from - as a result of this experience - here is the Positives steps and learnt lessons we gleaned from it..."
Do you know anything about What system it was? Or any detail as to what actually happened in that story (which is all true BTW)? No - you know the important aspects that a team made an assumption, didn't sanity check it and bad things happened and then you talk about what you learned from the experience.
Most professionals know from bitter experience that sometimes things go wrong - the way to frame it, is how you or the company learned from it.
That would be me suggestion, abstract as much of the information out of it, so only the key points of 'something went wrong' and 'here's what we learned from it' remain