Android - corrupt video after downloaded

After downloading a video file from the Dropbox android application, the file gets corrupted.

Background why I want to do this:

In my android application, the user can select a video file from Dropbox (if they have the app installed on their device). The Dropbox application downloads the file after the user selects it and I get a Uri of that file, I then create a new file for me to use in my application.

At first I thought that I made a mistake in my code while copying the file, but I went to the Dropbox download location (data/com.dropbox.android/files/u4378374/scratch/myFolder) and I tested and got the same result. Thats when I knew that the fault is with the Dropbox application and not my application.

I also tested by downloading a file from my computer and the video is not corrupted, I'm not sure if Dropbox applies some sort of compression when downloading a file from the android application?

I have asked a question about this on stackoverflow.com, here is the link to that question (Please see edit 1) - https://stackoverflow.com/questions/55686381/copying-file-from-dropbox-makes-the-file-corrupt

Can someone please adive me on what I should do and why this happens?