How to prevent report overwrite with sandbox?

SOLVED

Hi all,

I have this situation below.

I generate new sandbox to send to customer. In the sandbox, I have few reports, lets say Report A, B, and C. Report A and B is not modified on this sandbox. So lets say report A and B is version 1. I only modified the Report C.

On the customer Server, my customer have make amendment on Report A and B such as adding company logo etc. So lets say the reports on customer server is version 2. When he update the add on with my sandbox, the reports version 2 is being replaced with version 1 from my sandbox. And now he have to redo the changes that he did. How can I prevent this?

Thank you.