diff --git a/scripts/ai/SelfUnloadHelper.lua b/scripts/ai/SelfUnloadHelper.lua
index 69d56988..01e65eeb 100644
--- a/scripts/ai/SelfUnloadHelper.lua
+++ b/scripts/ai/SelfUnloadHelper.lua
@@ -35,6 +35,10 @@ SelfUnloadHelper.maxDistanceFromField = 20
 ---@return table|nil best fill node of trailer
 ---@return number|nil distance of trailer from myVehicle
 function SelfUnloadHelper:findBestTrailer(fieldPolygon, myVehicle, implementWithPipe, pipeOffsetX)
+    if fieldPolygon == nil or #fieldPolygon == 0 then
+        CpUtil.errorVehicle(myVehicle, 'Field polygon is nil or empty, can\'t find a trailer to unload to')
+        return nil
+    end
     local bestTrailer, bestFillUnitIndex, bestFillType
     local minDistance = math.huge
     for _, otherVehicle in pairs(g_currentMission.vehicleSystem.vehicles) do
@@ -125,7 +129,6 @@ end
 ---@param fillRootNode number|nil optional fill node for the trailer, must not be nil if bestTrailer is not nil
 function SelfUnloadHelper:getTargetParameters(fieldPolygon, myVehicle, implementWithPipe, objectWithPipeAttributes,
                                               bestTrailer, fillRootNode)
-
     if not bestTrailer then
         -- no trailer passed in, let's find one
         bestTrailer, fillRootNode = SelfUnloadHelper:findBestTrailer(fieldPolygon, 
diff --git a/scripts/ai/strategies/AIDriveStrategyCombineCourse.lua b/scripts/ai/strategies/AIDriveStrategyCombineCourse.lua
index 841d1a56..dda0eeda 100644
--- a/scripts/ai/strategies/AIDriveStrategyCombineCourse.lua
+++ b/scripts/ai/strategies/AIDriveStrategyCombineCourse.lua
@@ -76,10 +76,6 @@ AIDriveStrategyCombineCourse.isAAIDriveStrategyCombineCourse = true
 function AIDriveStrategyCombineCourse:init(task, job)
     AIDriveStrategyFieldWorkCourse.init(self, task, job)
     AIDriveStrategyCourse.initStates(self, AIDriveStrategyCombineCourse.myStates)
-    --- Combine needs a field polygon for the self-unload to work. Although it is a user setting, but it can be
-    --- changed during the work, so we always require the field polygon, regardless of the setting, as it is checked
-    --- only after starting the CP driver.
-    self.state = self.states.WAITING_FOR_FIELD_BOUNDARY_DETECTION
     self.fruitLeft, self.fruitRight = 0, 0
     self.litersPerMeter = 0
     self.litersPerSecond = 0
@@ -243,17 +239,20 @@ function AIDriveStrategyCombineCourse:getDriveData(dt, vX, vY, vZ)
         self:setMaxSpeed(0)
     end
 
-    if self.state == self.states.INITIAL and self.vehicle:cpGetFieldPolygon() == nil then
-        self:setMaxSpeed(0)
-        self.state = self.states.WAITING_FOR_FIELD_BOUNDARY_DETECTION
+    --- Combine may need the field polygon for the self-unload to work, so if by now we don't have one
+    --- and the field boundary detection is not running, start it. This can happen if the combine wasn't started
+    --- directly, such as as it was driving to the field and then switched strategy
+    if not self.vehicle:cpIsFieldBoundaryDetectionRunning() and self.vehicle:cpGetFieldPolygon() == nil then
         self:startFieldBoundaryDetection()
     end
 
-    if self.state == self.states.WAITING_FOR_FIELD_BOUNDARY_DETECTION then
-        self:setMaxSpeed(0)
+    if self.vehicle:cpIsFieldBoundaryDetectionRunning() then
+        if self.settings.selfUnload:getValue() then
+            -- don't have the field boundary yet, and self unload is selected, don't move
+            self:setMaxSpeed(0)
+        end
         if self:waitForFieldBoundary() then
             self:debug('Have field boundary now.')
-            self.state = self.states.INITIAL
         end
     elseif self.state == self.states.WORKING then
         -- Harvesting