Certainly possible in one way or another. They could be using hydrophobic excipients like magnesium stearate for lubrication in too high a quantity &/or mixing the magnesium stearate etc into the powder blend for too long. That would increase the hardness of the tablets for the same amount of pressing force. It could also slow down or reduce the disollution of the tablet as particles would be coverd in a waxy, hrdrophobic coating. You could be literally flushing some of the drug down the toilet everytime you take a dump.