diff --git a/app/controllers/challenge_assignments_controller.rb b/app/controllers/challenge_assignments_controller.rb
index b382c2e269..e59c727cb8 100644
--- a/app/controllers/challenge_assignments_controller.rb
+++ b/app/controllers/challenge_assignments_controller.rb
@@ -149,6 +149,7 @@ def set
     end
 
     ChallengeAssignment.update_placeholder_assignments!(@collection)
+    ChallengeAssignment.split_off_write_in_giver_assignments!(@collection)
     if @assignments.empty?
       flash[:notice] = "Assignments updated"
       redirect_to collection_potential_matches_path(@collection)
diff --git a/app/models/challenge_assignment.rb b/app/models/challenge_assignment.rb
index 347473b8b0..cdedd71f65 100755
--- a/app/models/challenge_assignment.rb
+++ b/app/models/challenge_assignment.rb
@@ -496,4 +496,24 @@ def self.update_placeholder_assignments!(collection)
       end
     end
   end
+
+  # create fresh new assignments for pinch hitters assigned alongside existing offer signups
+  def self.split_off_write_in_giver_assignments!(collection)
+    collection.assignments.each do |assignment|
+      assignment.split if assignment.double_assigned?
+    end
+  end
+
+  def double_assigned?
+    pinch_hitter && offer_signup && pinch_hitter.user != offering_user
+  end
+
+  def split
+    new_assignment = self.dup
+    new_assignment.offer_signup = nil
+    new_assignment.save!
+
+    self.pinch_hitter = nil
+    save!
+  end
 end
diff --git a/spec/controllers/challenge_assignments_controller_spec.rb b/spec/controllers/challenge_assignments_controller_spec.rb
index 3e87664965..5eb26a1677 100644
--- a/spec/controllers/challenge_assignments_controller_spec.rb
+++ b/spec/controllers/challenge_assignments_controller_spec.rb
@@ -146,6 +146,36 @@
         end
       end
 
+      context "when an assignment has both an offer and a pinch hitter" do
+        let(:params) do
+          {
+            collection_id: collection.name,
+            challenge_assignments: {
+              assignment.id => {
+                request_signup_pseud: signup1.pseud.byline,
+                offer_signup_pseud: signup2.pseud.byline,
+                pinch_hitter_byline: other_user.pseuds.first.byline
+              }
+            }
+          }
+        end
+
+        it "creates a new assignment for the pinch hitter" do
+          PotentialMatch.create(request_signup: signup1,
+                                offer_signup: signup2,
+                                collection: collection)
+
+          put :set, params: params
+
+          assignment.reload
+          expect(assignment.pinch_hitter).to be_nil
+
+          pinch_hitter_assignment = collection.assignments.find_by(pinch_hitter_id: other_user.pseuds.first.id)
+          expect(pinch_hitter_assignment).to be_present
+          expect(pinch_hitter_assignment.offer_signup).to be_nil
+        end
+      end
+
       context "when assignments have been sent" do
         let(:gift_exchange) { create(:gift_exchange, assignments_sent_at: Faker::Time.backward) }