Mysql Database Migration failed

I've been trying to migrate a large mysql 5.6 database between two amazon RDS instances using mysql workbench 6.2. It initially failed because the key_buffer_size on the target server was too low. After increasing the buffer most of the tables migrated successfully - except for a handful, each approaching ~3million rows in size.

I've been searching around on google for a good answer but nothing concrete has surfaced yet. Any tips are much appreciated!