What is the most common issue for the highest priority complaints?
most common refers to max(count(issue)); highest priority refers to priority = 2
SELECT T1.Issue FROM events AS T1 INNER JOIN callcenterlogs AS T2 ON T1.`Complaint ID` = T2.`Complaint ID` WHERE T2.priority = 2 GROUP BY T1.Issue ORDER BY COUNT(T1.Issue) DESC LIMIT 1