Experience Design overwriting existing a URL

I've been generating prototypes to share with others in my office for different product modules. These are separate files. Previously completed and shared URL's have gotten overwritten by newer files. The URL's are not the same yet when others will reference one that was for Project A it now shows Project B. I've cleared my cache but this continues to happen.

Can you please tell me what is causing this issue and how do I prevent it from happening? We would like to share some of these URL's with customers so preservation is very important.

Thanks