In case the added location on the invoice will be removed upon saving it, then I suggest clearing the browser's cache. There are times that the browser you're using has information stored that's stopping or causing this error.
I recommend using a private browser or an incognito window when trying to process it. Then, you may clear the cache in the one that you're currently using if it works. Here’s how:
For Chrome, press Ctrl+Shift+N.
For Internet Explorer or Firefox, press Ctrl+Shift+P.