Videos ruined after a while

Hi all,

I'm using Adobe Premiere Rush to create videos.

Everything works fine when I'm creating them and a few days later. 

But when I open the video projects after a few weeks, the videos are ruined. The audio is out of sync, the clips are distorted and lagging, and it's just ruined. So i can never use it again.

What is causing this? I'm storing the videos and the clips in Dropbox and I have the Dropbox App installed on my Macbook Pro.