Do I need transit visa?

Hi there,

I will fly to Vietnam and I have a flight change in Shenzhen. As per my travel agent I will have to pick up my luggage and check it in again. That means leaving "duty free" area. I have not found Shenzhen on the list of airports where I can ask for transit visa at the spot so I should sort it out before departure, is that correct?

I am holder of EU (CZE) passport and have about 6 hours of waiting time.

Any advice will be greatly appreciated!

Thank you :)