The database updater for 3.0.9 release candidates created a attempt_id primary key that was unecessary and too small. The database updater was later changed to not add this column when upating from older versions. The db_tools class at the time was not capable of correctly dropping a primary key column. So dropping the attempt_id column on boards that were updated to a 3.0.9 RC or installed with a 3.0.9 RC version was delayed until 3.0.10-RC1.