I occasionally get return of broken/damaged goods some of which are damaged due to use or manufacturing faults.
Do you have the products and ship them out yourself? If not then you should work out something with your shipper on damaged goods. That's what we do.
Damage due to use is clearly a manufacturer/user issue.
We are a U.S. based reseller too.
We purchase our items through a wholesaler.
Our position is that all warranty or manufacturing defects are the ultimate responsibility of the manufacturer.
We do however, go back to the manufacturer on the customers behalf when necessary.
Additionally on our site we are very clear about damaged goods, in that if they sign for it without inspecting it, then they take upon the responsibility of the goods and if there's a problem, it's on them; but that we would of course be there to help them as much as what makes good business sense.
From our site: ("example.com" is a fictitous company)
Warranty
Products sold by example.com are covered by Manufacturer's warranties and subject to their terms. There are NO other warranties, either expressed or implied by example.com. We will at your request work with you and the manufacturer to an extent that a resolution has been determined. At no time is example.com responsible for covering any warranty claims on any products we sell.
If you use a supplier or order direct from the manufacturer it is not uncommon to get a discounted or percentage reduction in your purchase price from them to handle product issues you described. In doing such, your company alone would be responsible for replacement of the product, etc.