These dropouts did not cause the motor to slow down significantly as evidenced by the fact that the inactive  (A-String) voltage remained relatively constant, and the transition time was nominal. Because the unit  transitioned normally, the spikes in current were not flagged by the test team for evaluation. After this initial indication of an issue, the latch proceeded through the remainder of the TVAC test as well  as the first 5 cycles of the Thermal Cycle test without issue. During the sixth hot thermal cycle, the latch  again exhibited current spikes. This occurrence was much more severe, with more spikes resulting in a  slower transition time for both the A and B strings. Although this was abnormal performance, it was within  the threshold established for compliance and was not flagged by the test team.  During the subsequent cold operation, the unit failed to meet the transition time requirement. Review of the  data showed no current spikes, but the inactive string voltage was abnormally low, indicating a slow motor  speed. At this point troubleshooting of the failure began, which included inspections for debris (none  identified) and operation of the motor at temperature with data recorded at a higher sampling rate. The  motor operated inconsistently, where some operations were nominal whereas other operations had current  spikes. The motor/controller supplier reviewed this data and concluded that this current signature was  consistent with either a failed HED, a failed HED circuit in the controller, or a break in the wiring for the  HEDs between the two.  At this time, it was determined that the motor and controller should be returned to the supplier for further  investigation. Prior to shipment, the wires between the motor and controller were inspected to confirm no  wires were damaged or cut.  Upon receipt of the motor/controller, the supplier  replicated the failure observed during the  acceptance test. The motor and controller were  separated and tested individually to isolate the  failure. This individual testing showed the motor as  the source of the failure and that a teardown and  inspection of the motor would be required to  determine the cause of the failure. However, based  on the experience of Failure 1, where the teardown  process was too destructive, additional NDI (Non  Destructive Inspections) were performed prior to  teardown. Using Time Domain Reflectometry  inspection techniques, a break in the wiring in the  vicinity of the HED was identified, either in the HED itself, the solder joint at the circuit board, or  immediately adjacent to the solder joint. Initial XRay imaging through the casing of the motor failed  to provide meaningful images. Therefore, a careful  disassembly of the motor was performed, with  additional care taken to avoid heat related damage  that occurred during the disassembly of the motor in  Failure 1. High-resolution imaging and X-Ray  imaging was performed on the HEDs, which ultimately revealed the cause of the failure, cracks in the HED  and HED lead wires, as shown in Figure 5 (items A, B, and C) and Figure 6 (item A). The imaging also  revealed the presence of large voids in the potting compound used to fix the HEDs in place, as shown in  Figure 5 (item D) and Figure 6 (item B).  Root Cause  Once the fault had been isolated to the HED leads, a root cause analysis was performed to determine why  the cracks in the leads had occurred with two contributing factors identified. First, it was noted that the HED  leads were splayed apart during assembly to align with holes in the printed circuit board, as shown in  AB C D Figure 5. HED X-Ray Showing Cracked Lead  NASA/CP—2018-219887 491