It always a waste of time to undo a reconciliation due to minor errors.  Just fix the prior posting errors, then fix the prior reconciliation to match.

Fixing the prior postings is up to you - just make them right. While doing this you will get warnings not to change reconciled items - do it anyway (this assumes you know what your doing and will finish the next step !!!).

Now fix the reconcilation - you cant edit so do a new reconciliation using the same closing balance and date that was used the first time you did it.  Once you 'hide items after the statement date' then only things left will be your new (or changed) entries, plus the prior uncleared items.  Now reconcile the changes.