>The onus is on the customers to realize that the has been an issue,
If the customer has no issues there are no issues right?
>Then there are shipping costs, likely the customers bought it from a local retainer, that may or may not be in business...
Again it's an HP and you send it directly to them, the MANUFACTURER has to cover all costs. Your retailer has not made the update so he should have nothing to do with it.
>The endless emails and phone calls.
One email: My printer (serial-number) worked for two years with that toner, since your update it's not working anymore (error blablabla), roll back that update or send me a shipping label.
>Overall the customers are not in any position of power without a forced recall.
Time to change that then right? Restore the functionality of my device or take it back.
You are making a problem where no are.