duplicate project edits

Hi

I have a project that is about 10 mins long and I want to make a duplicate of this project to make a condensed version of it. When I duplicate the project any edits I make in the duplicate project then show up in the original project. I have tried duplicating as a snapshot also and the same thing happens. I have read this happens if you use compound clips in your project but I'm pretty sure I'm not using compound clips.

Any help would be much appreciated - thanks in advance!