When high-voltage cable assemblies and their connectors fail, it is generally catastrophic. This is because a dielectric breakdown has occurred.
Dielectric breakdowns happen when the voltage stress is significant enough to cause an arc through the dielectric between the conductor and ground. The failure is catastrophic because the current flow through the dielectric leaves voids filled with carbon. The dielectric will no longer be able to withstand the required voltage, and in some cases, voltage can’t be raised.