diff --git a/models/base.rb b/models/base.rb
index d58438033..ba27e887c 100644
--- a/models/base.rb
+++ b/models/base.rb
@@ -80,7 +80,7 @@ def self.has_many(name, options = {})
       # Array and other objects that are not based on Models::Base class cannot have id methods
       if options[:class_name]&.start_with? 'Models::'
         define_method(ids_function_name) do
-          self[ids_function_name]
+          self[ids_function_name] ||= self[name]&.map(&:id) || []
         end
 
         define_method("#{ids_function_name}=") do |vals|
@@ -110,7 +110,7 @@ def self.belongs_to(name, options = {})
       # Array and other objects that are not based on Models::Base class cannot have id methods
       if options[:class_name]&.start_with? 'Models::'
         define_method(id_function_name) do
-          self[id_function_name]
+          self[id_function_name] ||= self[name]&.id
         end
 
         define_method("#{id_function_name}=") do |val_id|
diff --git a/wrappers/wrapper.rb b/wrappers/wrapper.rb
index c889eb898..ece8581a8 100644
--- a/wrappers/wrapper.rb
+++ b/wrappers/wrapper.rb
@@ -977,8 +977,6 @@ def simplify_vehicle_pause(vrp, result = nil, options = { mode: :simplify })
             vehicle.timewindow.end -= rest.duration if vehicle.timewindow&.end
           }
 
-          vehicle[:simplified_rest_ids] = vehicle[:rest_ids].dup
-          vehicle[:rest_ids] = []
           vehicle[:simplified_rests] = vehicle.rests.dup
           vehicle.rests = []
         }
@@ -988,11 +986,9 @@ def simplify_vehicle_pause(vrp, result = nil, options = { mode: :simplify })
       when :rewind
         # take the modifications back in case the vehicle is moved to another sub-problem
         vrp.vehicles&.each{ |vehicle|
-          next unless vehicle[:simplified_rest_ids]&.any?
+          next unless vehicle[:simplified_rests]&.any?
 
-          vehicle[:rest_ids].concat vehicle[:simplified_rest_ids]
-          vehicle[:simplified_rest_ids] = nil
-          vehicle.rests.concat vehicle[:simplified_rests]
+          vehicle.rests += vehicle[:simplified_rests]
           vehicle[:simplified_rests] = nil
 
           vehicle.rests.each{ |rest|
@@ -1002,14 +998,14 @@ def simplify_vehicle_pause(vrp, result = nil, options = { mode: :simplify })
         }
 
         if vrp[:simplified_rests]
-          vrp.rests.concat vrp[:simplified_rests]
+          vrp.rests += vrp[:simplified_rests]
           vrp[:simplified_rests] = nil
         end
       when :patch_result
         # correct the result with respect to simplifications
         pause_and_depot = %w[depot rest].freeze
         vrp.vehicles&.each{ |vehicle|
-          next unless vehicle[:simplified_rest_ids]&.any?
+          next unless vehicle[:simplified_rests]&.any?
 
           route = result[:routes].find{ |r| r[:vehicle_id] == vehicle.id }
           no_cost = route[:activities].none?{ |a| pause_and_depot.exclude?(a[:type]) }