Hi @tboy123, thanks for the additional details. It sounds like you’re using custom code on your site, is that correct?
If it is, can you temporarily disable or remove the code, and then complete an order to see if the issue still persists? If the issue goes away, then you’ll need to audit the custom code or ask the developer that created it to inspect it to see why it behaves differently.
Even if no overt changes were made, plugins and themes constantly roll out new versions, and with it can come new ways to do things, that may not have existed when the custom code was created. Developers usually avoid this scenario by staying up to speed via our Developer Resources (Stay updated).
Let us know if the above helps, or if you need further assistance.