How many orders' does he have that it takes him a couple years to get each one out the door? I'm sorry, but working full time is no excuse for holding on to people’s stuff for years on end. At the very least he could shove it in a box and send it back to them, which takes minimal effort.
And if it’s a legitimate problem, why not update people and correspond with them? Nope, shady dealings come with shady business.