I was refactoring my code, this should be a regular thing. But using Ext.Loader to resolve my classes to load this turned out to be a tricky thing:

At first I had my classes called like ProductStore and ProductModel. However, Ext 4 magic turned them into getters like ProductStoreStore and ProductModelModel. So, now I have in my IDE multiple Product files open. Anyway, in a controller I first supplied the full path class name like:
stores: ['GenForm.store.product.ProductStore']. I changed this in stores: ['product.Product'].

In a completely different part of my app I used this store in a form combobox supplying store: 'GenForm.store.product.Product'. I did change the name from ProductStore to Product.
You will probably already see the problem. But figuring this out is in practice really not simple!

I cannot see why supplying the full classname should not continue to work, even when in a controller you used the abbreviated version of that name.

By the way you get something cryptical like: me.store not defined in Loader.js(line 1109)