Duplicating the Precomposed composition changes original composition

You get a unique copy if you duplicate a composition in the Project Panel. It looks like the comp you duplicated also has nested compositions. You need to duplicate all of them and then replace the duplicates in the main duplicated comp. It looks like you are trying to duplicate Layer 12 named Passion Fruit Sorbet, originally named Comp 8, but I don't see a duplicate in the project panel. I'm not sure what you actually did.

You can spend a few dollars for True Comp Duplicator - aescripts.com to automate this process, or you can open up the flow chart to use as a guide and figure out which nested comps are in the original duplicated composition, duplicate them all, then replace them in the original Duplicated comp. The process can get very complicated in a project like this.