Shield grounding location for an STP cable in a balanced system
Best practice is to ground the shield at the receiver end. This of course assumes that the transmit end (the sending end) is designed adequately. 

Not grounding the shield raises the net capacitance of the inner conductors to any aggressor electric field and creates higher common mode voltages on the differential pair and, due to small impedance imbalances on the differential pair, some of that common mode interference is converted to differential interference. 

Hence not grounding the shield creates more interference on the otherwise pure signal and deteriorates the receiver amplifier’s ability to reject common mode noise.