PDO driver issue - multiple insert

The CI 2.x branch has been 'End Of Life' since October 2015. In my opinion you should spend some time to upgrade your application to the 3.x branch before you ask for support. Seriously, it's time to move on.

Alot of bugs (and don't forget about security fixes!) have been resolved in all new versions. It could very well be that after you upgrade your application your database issue is already resolved.