diff --git a/src/blenderbim/blenderbim/bim/module/sequence/prop.py b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
index e7a205f8a5..556878e411 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
@@ -117,7 +117,6 @@ def updateTaskTimeDateTime(self, context, startfinish):
             return "-"
         return time.strftime("%d/%m/%y")
 
-    startfinish_key = "Schedule" + startfinish.capitalize()
     startfinish_value = getattr(self, startfinish)
 
     if startfinish_value == "-":
@@ -141,6 +140,7 @@ def updateTaskTimeDateTime(self, context, startfinish):
         task_time = ifcopenshell.api.run("sequence.add_task_time", self.file, task=task)
         Data.load(IfcStore.get_file())
 
+    startfinish_key = "Schedule" + startfinish.capitalize()
     if Data.task_times[task_time.id()][startfinish_key] == startfinish_datetime:
         canonical_startfinish_value = canonicalise_time(startfinish_datetime)
         if startfinish_value != canonical_startfinish_value:
@@ -154,10 +154,9 @@ def updateTaskTimeDateTime(self, context, startfinish):
     )
     Data.load(IfcStore.get_file())
     bpy.ops.bim.load_task_properties()
-    setattr(self, startfinish, canonicalise_time(startfinish_datetime))
 
 
-def updateTaskduration(self, context):
+def updateTaskDuration(self, context):
     props = context.scene.BIMWorkScheduleProperties
     if not props.is_task_update_enabled:
         return
@@ -224,7 +223,7 @@ class Task(PropertyGroup):
     is_selected: BoolProperty(name="Is Selected")
     is_expanded: BoolProperty(name="Is Expanded")
     level_index: IntProperty(name="Level Index")
-    duration: StringProperty(name="Duration", update=updateTaskduration)
+    duration: StringProperty(name="Duration", update=updateTaskDuration)
     start: StringProperty(name="Start", update=updateTaskTimeStart)
     finish: StringProperty(name="Finish", update=updateTaskTimeFinish)
     calendar: StringProperty(name="Calendar")
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
index 1efc2aef3f..bbe679bbf3 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
@@ -12,9 +12,9 @@ class Usecase:
 
     def execute(self):
         self.calendar_cache = {}
-        self.cascade_task(self.settings["task"])
+        self.cascade_task(self.settings["task"], is_first_task=True)
 
-    def cascade_task(self, task):
+    def cascade_task(self, task, is_first_task=False):
         if not task.TaskTime:
             return
 
@@ -88,13 +88,13 @@ class Usecase:
             )
             if potential_finish > finish:
                 start_ifc = ifcopenshell.util.date.datetime2ifc(start, "IfcDateTime")
-                if task.TaskTime.ScheduleStart == start_ifc:
+                if task.TaskTime.ScheduleStart == start_ifc and not is_first_task:
                     return
                 task.TaskTime.ScheduleStart = start_ifc
                 task.TaskTime.ScheduleFinish = ifcopenshell.util.date.datetime2ifc(potential_finish, "IfcDateTime")
             else:
                 finish_ifc = ifcopenshell.util.date.datetime2ifc(finish, "IfcDateTime")
-                if task.TaskTime.ScheduleFinish == finish_ifc:
+                if task.TaskTime.ScheduleFinish == finish_ifc and not is_first_task:
                     return
                 task.TaskTime.ScheduleFinish = finish_ifc
                 task.TaskTime.ScheduleStart = ifcopenshell.util.date.datetime2ifc(
@@ -109,7 +109,7 @@ class Usecase:
         elif finishes:
             finish = max(finishes)
             finish_ifc = ifcopenshell.util.date.datetime2ifc(finish, "IfcDateTime")
-            if task.TaskTime.ScheduleFinish == finish_ifc:
+            if task.TaskTime.ScheduleFinish == finish_ifc and not is_first_task:
                 return
             task.TaskTime.ScheduleFinish = finish_ifc
             task.TaskTime.ScheduleStart = ifcopenshell.util.date.datetime2ifc(
@@ -124,7 +124,7 @@ class Usecase:
         elif starts:
             start = max(starts)
             start_ifc = ifcopenshell.util.date.datetime2ifc(start, "IfcDateTime")
-            if task.TaskTime.ScheduleStart == start_ifc:
+            if task.TaskTime.ScheduleStart == start_ifc and not is_first_task:
                 return
             task.TaskTime.ScheduleStart = start_ifc
             task.TaskTime.ScheduleFinish = ifcopenshell.util.date.datetime2ifc(