Not 100% Accurate Means Too Inaccurate

I paid for it and used it for a year on my webshop. Indeed, there are no wrong addresses anymore.
I eventually removed and moved to another solution rafter a customer entered a valid address and the plugin would by no means allow him to submit his order.
There might be only few cases like this, but I would expect a zero-error-tolerance in a tool like this.
Maybe as a suggestion: If the plugin is unsure for a certain address, why not popping up a message and ask the customer whether he is sure that address is correct, and then anyway allow to submit?