A system configured to be arranged aboard an unmanned aerial vehicle (UAV) , the system comprising: a tether disposed on a spool ; a motor , wherein operating the motor in a first mode and a second mode, respectively, counters and assists unwinding of the tether due to gravity; a payload coupling apparatus structured to mechanically couple the tether to a payload; a control system configured to control the motor to carry out tethered delivery of the payload; wherein, during a process of picking up the payload to be delivered and while a UAV comprising the system is over or near to a pickup location, the control system is further configured to: responsive to a determination that the payload coupling apparatus is mechanically coupled to the payload, operate the motor to retract the tether and lift the payload toward the UAV; while retracting the tether with the payload coupled thereto, detect an error condition when both (i) a motor current of the motor is greater than a threshold current and (ii) an unwound length of the tether is greater than a threshold length; make an attempt to correct the error condition by operating the motor to unwind the tether and then resume retracting the tether; and determine that a predetermined number of attempts to correct the error condition have been made without successfully correcting the error condition, and responsively end the process of picking up the payload and initiate a payload delivery process to return the payload to the ground at or near the pickup location. a tether disposed on a spool ; a motor , wherein operating the motor in a first mode and a second mode, respectively, counters and assists unwinding of the tether due to gravity; a payload coupling apparatus structured to mechanically couple the tether to a payload; a control system configured to control the motor to carry out tethered delivery of the payload; wherein, during a process of picking up the payload to be delivered and while a UAV comprising the system is over or near to a pickup location, the control system is further configured to: responsive to a determination that the payload coupling apparatus is mechanically coupled to the payload, operate the motor to retract the tether and lift the payload toward the UAV; while retracting the tether with the payload coupled thereto, detect an error condition when both (i) a motor current of the motor is greater than a threshold current and (ii) an unwound length of the tether is greater than a threshold length; make an attempt to correct the error condition by operating the motor to unwind the tether and then resume retracting the tether; and determine that a predetermined number of attempts to correct the error condition have been made without successfully correcting the error condition, and responsively end the process of picking up the payload and initiate a payload delivery process to return the payload to the ground at or near the pickup location. responsive to a determination that the payload coupling apparatus is mechanically coupled to the payload, operate the motor to retract the tether and lift the payload toward the UAV; while retracting the tether with the payload coupled thereto, detect an error condition when both (i) a motor current of the motor is greater than a threshold current and (ii) an unwound length of the tether is greater than a threshold length; make an attempt to correct the error condition by operating the motor to unwind the tether and then resume retracting the tether; and determine that a predetermined number of attempts to correct the error condition have been made without successfully correcting the error condition, and responsively end the process of picking up the payload and initiate a payload delivery process to return the payload to the ground at or near the pickup location. <EOS>