Exploding 49A Toner Cartridges

[Stephen2020]

I purchased about 30 HP 49A Q5949A Black Toner Cartridges from a company that no longer needed them. They are in sealed, clean, undamaged original HP boxes.  I have sold about 12 of them on Ebay and 6 of the 12 buyers have indicated that when they installed the toner cartridge it "exploded" sending toner everywhere inside of their printer.  If this had happened once, I would have assumed the buyer did something incorrectly, but for 6 different people to have the same problem in a period of a few days?  I shipped these by either FedEx Ground or USPS Priority Mail.  I wrapped the HP box in bubble wrap and placed inside of another box to protect it during shipping.  Any suggestions as to what may be going on with these cartridges?  Was there a recall at some point?  These are several years old, but are new in the sealed box as I said before.  Thanks!

[Repairatrooper]

Depending on storage conditions the sealer blades that control toner can fail and result in toner running out of the toner bin and past the drum unit into the printer. We usually see this on cartridges that are 10+ years old but extreme cold or heat can accelerate the decline.