"If there is a way to find out what version of English a ProZ.com member uses most, I don't know what it is."
It's called being a regular contributor (no offense).
As for the rest, I asked the American half of this household. Answer: Why would they be so inefficient as to deliver it in three separate packages?
I think we can only agree to disagree here. Your solution isn't very clear to me. Since I'm not the only one who thinks so, I don't believe it's a good choice. Customers are not mind readers either.
Also, you did
not just repeat what you said in your answer. Your suggestion was 1 shipment being divided into 5 smaller
shipments (not supported by the dictionary link).
Now, it's one shipment being divided into 5
packages. That's probably the issue. It's still one order and one shipment, but you get five items and not just one.
Additionally, I don't see a problem with supply; "unable to/cannot supply you with" is more or less a standard phrase: "If we cannot supply you with the goods you have ordered, we reserve the right to supply you with substitute goods of similar quality and function."
https://timprestage.co.uk/shop/terms.aspBest