SLW is not a miner but a dealer, a middle man if you want to call it that. If the producers don't have enough silver ready for delivery, slw is out of luck and can sit and hope that there will be more silver for them in the coming weeks, months dependent on the suppliers.
I would imagine that if slw continues to be short on silver deliveries for some time, they would invoke parts of their contracts to force the supplier(s) to cover the losses due to the contractual obligation of deliverable silver per quarter, but I'm sure slw won't play hardball every quarter or unless they have to since they understand that you can't guarantee silver outputs or timely deliveries on timely basis as long as the suppliers are doing their best to fulfill the contract with slw.
SLW had these problems for a long time, nothing new. Maybe next quarter there will be more sales than expected or not, either way, slw price has done better than majority of miners so there is no point of crying about the price of slw at this point.
Take profits where you can, buy on corrections.