Index: app/models/sprint.rb
===================================================================
--- app/models/sprint.rb        (.../v0.13.2~5) (revision 48)
+++ app/models/sprint.rb        (.../v0.13.2~6) (revision 52)
@@ -57,6 +57,15 @@
     issues.where(conditions).order(order).select{|issue| issue.visible?}
   end

+  def normalized_pbis
+    normalize_positions(pbis)
+  end
+
+  def release_position(pbi)
+    normalize_positions(pbis, pbi)
+    nil
+  end
+
   def story_points
     pbis.collect{|pbi| pbi.story_points.to_f}.compact.sum
   end
@@ -219,6 +228,20 @@

 private

+  def normalize_positions(issues, issue_to_ignore = nil)
+    new_position = 1
+    issues.each do |issue|
+      unless issue == issue_to_ignore
+        unless issue.position == new_position
+          issue.position = new_position
+          issue.save!
+        end
+        new_position += 1
+      end
+    end
+    issues
+  end
+
   def update_project_product_backlog
     if is_product_backlog?
       project.product_backlog = nil
Index: app/controllers/product_backlog_controller.rb
===================================================================
--- app/controllers/product_backlog_controller.rb       (.../v0.13.2~5) (revision 48)
+++ app/controllers/product_backlog_controller.rb       (.../v0.13.2~6) (revision 52)
@@ -124,7 +124,7 @@
   end

   def find_pbis
-    @pbis = @product_backlog.pbis
+    @pbis = @product_backlog.normalized_pbis
   rescue
     render_404
   end
Index: lib/scrum/issue_patch.rb
===================================================================
--- lib/scrum/issue_patch.rb    (.../v0.13.2~5) (revision 48)
+++ lib/scrum/issue_patch.rb    (.../v0.13.2~6) (revision 52)
@@ -19,7 +19,7 @@

         safe_attributes :sprint_id, :if => lambda {|issue, user| user.allowed_to?(:edit_issues, issue.project)}

-        before_save :update_position, :if => lambda {|issue| issue.sprint_id_changed? and issue.is_pbi?}
+        before_save :update_positions_on_sprint_change, :if => lambda {|issue| issue.sprint_id_changed? and issue.is_pbi?}

         before_save :update_sprint_of_children, :if => lambda {|issue| issue.sprint_id_changed? and issue.is_pbi?}

@@ -224,10 +224,8 @@
             case position
               when "top"
                 move_issue_to_the_begin_of_the_sprint
-                save!
               when "bottom"
                 move_issue_to_the_end_of_the_sprint
-                save!
               when "before", "after"
                 if other_pbi_id.nil? or (other_pbi = Issue.find(other_pbi_id)).nil?
                   raise "Other PBI ID ##{other_pbi_id} is invalid"
@@ -239,17 +237,16 @@
                   move_issue_respecting_to_pbi(other_pbi, position == "after")
                 end
             end
+            self.save!
           end
         end

         def is_first_pbi?
-          min = min_position
-          return ((!(position.nil?)) and (!(min.nil?)) and (position <= min))
+          self == sprint.pbis.first
         end

         def is_last_pbi?
-          max = max_position
-          return ((!(position.nil?)) and (!(max.nil?)) and (position >= max))
+          self == sprint.pbis.last
         end

       protected
@@ -262,7 +259,7 @@

       private

-        def update_position
+        def update_positions_on_sprint_change
           if sprint_id_was.blank?
             # New PBI into PB or Sprint
             if @set_on_top
@@ -281,47 +278,55 @@
               # From Sprint to Sprint
               move_issue_to_the_end_of_the_sprint
             end
+            old_sprint.release_position(self)
           end
         end

-        def min_position
-          min = nil
-          sprint.pbis.each do |pbi|
-            min = pbi.position if min.nil? or (pbi.position < min)
+        def move_issue_to_the_begin_of_the_sprint
+          if first_pbi = sprint.pbis.first
+            move_issue_respecting_to_pbi(first_pbi, false)
+          else
+            self.position = 1
           end
-          return min
         end

-        def max_position
-          max = nil
-          sprint.pbis.each do |pbi|
-            max = pbi.position if max.nil? or (pbi.position > max)
+        def move_issue_to_the_end_of_the_sprint
+          if last_pbi = sprint.pbis.last
+            move_issue_respecting_to_pbi(last_pbi, true)
+          else
+            self.position = 1
           end
-          return max
         end

-        def move_issue_to_the_begin_of_the_sprint
-          min = min_position
-          self.position = min.nil? ? 1 : (min - 1)
-        end
-
-        def move_issue_to_the_end_of_the_sprint
-          max = max_position
-          self.position = max.nil? ? 1 : (max + 1)
-        end
-
         def move_issue_respecting_to_pbi(other_pbi, after)
-          self.position = other_pbi.position
-          self.position += 1 if after
-          self.save!
-          sprint.pbis(:position_above => after ? self.position : self.position - 1).each do |next_pbi|
-            if next_pbi.id != self.id
-              next_pbi.position += 1
-              next_pbi.save!
+          new_position = 1
+          sprint.pbis.each do |pbi|
+            unless pbi == self
+              if pbi == other_pbi
+                if after
+                  update_position(pbi, new_position)
+                  new_position += 1
+                  self.position = new_position
+                else
+                  self.position = new_position
+                  new_position += 1
+                  update_position(pbi, new_position)
+                end
+              else
+                update_position(pbi, new_position)
+              end
+              new_position += 1
             end
           end
         end

+        def update_position(pbi, new_position)
+          unless pbi.position == new_position
+            pbi.position = new_position
+            pbi.save!
+          end
+        end
+
         def update_sprint_of_children
           self.children.each do |child|
             unless child.closed?