This crash has constantly happened once a month with the same project which has manual intervention steps. Once the crash happens, I cannot stop or kill the task.
From this previous discussion (http://help.octopusdeploy.com/discussions/problems/46381-octopus-deploy-iserializable-type-octopussharedtasksactivityfailedexception-error), it is indicated that the bug is fixed with Octopus 3.2.11. We are using 3.4.14 and we are still seeing the same issue.