Use Rails standard naming: same name for the route and the method

app/controllers/spree/admin/orders_controller.rb

@@ -9,8 +9,8 @@ module Spree
       helper CheckoutHelper
 
       before_action :load_order, only: [:edit, :update, :fire, :resend,
-                                        :invoice, :print, :set_distribution]
-      before_action :load_distribution_choices, only: [:new, :edit, :update, :set_distribution]
+                                        :invoice, :print, :distribution]
+      before_action :load_distribution_choices, only: [:new, :edit, :update, :distribution]
 
       before_action :require_distributor_abn, only: :invoice
 
@@ -24,7 +24,7 @@ module Spree
         redirect_to spree.distribution_admin_order_path(@order)
       end
 
-      def set_distribution
+      def distribution
         return if order_params.blank?
 
         on_update

app/models/spree/ability.rb

@@ -274,7 +274,7 @@ module Spree
           # Enterprise User can access orders that are placed inside a OC they coordinate
           order.order_cycle&.coordinated_by?(user)
       end
-      can [:admin, :bulk_management, :managed, :set_distribution], Spree::Order do
+      can [:admin, :bulk_management, :managed, :distribution], Spree::Order do
         user.admin? || user.enterprises.any?(&:is_distributor)
       end
       can [:admin, :create, :show, :poll], :invoice

config/routes/spree.rb

@@ -89,8 +89,8 @@ Spree::Core::Engine.routes.draw do
         post :resend
         get :invoice
         get :print
-        get :distribution, to: 'orders#set_distribution'
-        put :distribution, to: 'orders#set_distribution'
+        get :distribution
+        put :distribution
       end
 
       collection do