If you’re not happy with the result, you don’t need to submit it. Diagnose the issue, remedy and recover, then do it again in a week or two. The SA doesn’t need to know what happened prior to official submission. Just call the last effort a “dress rehearsal” and move on.
If you do submit it, where and when do you find out if you passed?
And no, you cannot redo just one event. CFA is meant to be done as a set. Doing one event at a time gives you an unfair advantage. It’s essentially “super scoring” and that’s not permitted.