When you start to have issues with Spot N Paste, or if its not pasting correctly, its always a good idea to reset the store data before trying other trouble shooting techniques. 

Here is a video on how to do that.

If you want to completely remove a store or may have configured it mistakenly, you will have to do it from Spot n Center. Once the store has been synced with Spot n Center, whenever you try to reset, that specific store will be fetched and saved in your browser storage from Spot n Center. So it will be best to have it removed from Spot n Center as well. 

Once you are in Spot N Center you can find your synced stores under the Stores tab and delete it from here.