Products created via app are being assigned to a second inventory location unintentionally

Apologies in advance, as I may be describing the way inventory and locations work inaccurately.

We run a dropshipping app that creates products in our clients’ stores.

The inventory management for a given item is assigned to a location designated to the app. We’ve noticed issues fulfilling orders for these products, because the items are being assigned to a second location belonging to the store.

I’m confused as to what can do this? I know users can add a location to an item manually. Could another app be making these changes to the products created by my app?

In this screenshot, a store’s item is assigned to the app’s location (correctly), but also to the store’s location (incorrectly).