SLA workflows for incident records are getting their second-to-last activity (in this case, the event for 75% SLA duration elapsed) canceled. The user wanted to know why this is.
The user is experiencing a common racing issue (note that this behavior only happens for some records, not all).
When the "SLA Incident" workflow is opened, it was noted that there is a transition out from the SLA Percentage Timer activity "75 percent of SLA duration" to both the End activity and the Create Event "SLA warning notification" activity.
Intermittently, this will cause the user's Create Event activity to be canceled because the workflow will reach the "End" activity first before executing that activity.
To resolve the issue, the user should place a 2-second timer just before the End activity in their workflow (i.e. between the SLA Percentage Timer + Create Event and the End activity).
Placing the timer will prevent the workflow from ever canceling the final Create Event activity again.