Houghton Horns review for Zonos Duty and Tax

We have approximately a 20% error rate with packages shipped by Zonos and UPS Worldwide DDP. Over the past two months, three packages were sent back with no reason at all. I contacted support, and they said there was some kind of scanner error and I should just give the package back to UPS. I've done so, and two of the packages arrived safely. The last appears to be sitting in a UPS facility in California, not moving for four days. Worldwide DDP already takes 2-3 weeks to arrive, and if the package comes back to us and we have to wait four days to hear back from support - because they don't respond to emails promptly at all - it's taking more like 8 weeks for customers to get their packages. This is really frustrating for the customers, and then we're the ones who get the bad reviews, not Zonos or the carrier. Another package just got returned yesterday because "the address is incomplete. Attempts to obtain address information were unsuccessful." First, the address pops right up in Google Maps. It's fine. The customer has confirmed it. And second, neither us nor the customer heard anything about any issues with the address. They absolutely did not attempt to contact us before just pocketing our money and sending the package back. International shipments with Zonos make up about 2% of our total order volume, but about half of our shipping issues. We've contacted them and UPS multiple times and they say they'll look into it, but no one ever fixes the problem. As soon as our annual contract with Zonos runs out, we're cancelling and trying another option.