Symptoms
Sleeping tasks was seemingly not postponing the escalation of said task as would be the expectation.
Diagnoses
In this scenario the escalations had been set to the activity as opposed to the event and this is relevant. Activities contain events and can contain multiple events. Suppose that an activity contained two client events if one of the subsequent tasks were to be put to sleep should that have bearing on an escalation set at an activity level which controls multiple different events? No, a better approach is to set the escalation at the event level.
Resolution
Setting the escalations to occur at the event level should allow for the desired control.