Amazon Aurora MySQL5.6 Performance Schema column datatype modified and can't be corrected
This appears to be the result of the MySQL engine upgrade to version 5.7.3 or later, where the definition of some tables in the performance schema have changed.

If you were running standard MySQL, mysql_upgrade would have fixed that. You'll need to contact Amazon support for ways to upgrade your existing databases to the new engine version. 

In the worst case you'd need to create new copies of each affected database and move the data.