diff --git a/core/code_systems/serializers.py b/core/code_systems/serializers.py
index 20341bfc..d5270ff7 100644
--- a/core/code_systems/serializers.py
+++ b/core/code_systems/serializers.py
@@ -322,7 +322,7 @@ def update(self, instance, validated_data):
         concepts = validated_data.pop('concepts', [])
         new_version = validated_data.get('version')
 
-        if instance.version == new_version:
+        if instance.active_versions.filter(version=new_version):
             self._errors.update({'version': f'Version {new_version} already exists for CodeSystem'
                                             f' {instance.mnemonic}.'})
             return instance
diff --git a/core/concept_maps/serializers.py b/core/concept_maps/serializers.py
index 8934e033..d7d191b1 100644
--- a/core/concept_maps/serializers.py
+++ b/core/concept_maps/serializers.py
@@ -211,7 +211,7 @@ def update(self, instance, validated_data):
         mappings = validated_data.pop('mappings', [])
         new_version = validated_data.get('version')
 
-        if instance.version == new_version:
+        if instance.active_versions.filter(version=new_version):
             self._errors.update({'version': f'Version {new_version} already exists for CodeSystem'
                                             f' {instance.mnemonic}.'})
             return instance
diff --git a/core/importers/importer.py b/core/importers/importer.py
index dd1f0e39..fde4889e 100644
--- a/core/importers/importer.py
+++ b/core/importers/importer.py
@@ -11,7 +11,7 @@
 from zipfile import ZipFile
 
 from celery.result import AsyncResult, result_from_tuple
-from celery import group, chain
+from celery import group, chain, chord
 
 import ijson
 import requests
@@ -20,6 +20,7 @@
 from pydantic import BaseModel, computed_field, PrivateAttr
 
 from django.utils import timezone
+from rest_framework.exceptions import ValidationError
 
 from core import settings
 from core.common.serializers import IdentifierSerializer
@@ -30,6 +31,7 @@
 from core.importers.models import SourceImporter, SourceVersionImporter, ConceptImporter, OrganizationImporter, \
     CollectionImporter, CollectionVersionImporter, MappingImporter, ReferenceImporter, CREATED, UPDATED, FAILED, \
     DELETED, NOT_FOUND, PERMISSION_DENIED, UNCHANGED
+from core.orgs.models import Organization
 from core.sources.models import Source
 from core.users.models import UserProfile
 from core.collections.models import Collection
@@ -422,10 +424,12 @@ def schedule_tasks(self, tasks):
                                                           group_task['resource_type'], group_task['files'])
                                    .set(queue='concurrent'))
             if len(group_tasks) == 1:  # Prevent celery from converting group to a single task
-                group_tasks.append(bulk_import_subtask_empty.si())
-            chained_tasks |= group(group_tasks)
+                group_tasks.append(bulk_import_subtask_empty.si().set(queue='concurrent'))
+
+            chained_tasks |= chord(group(group_tasks), bulk_import_subtask_empty.si().set(queue='concurrent'))
         chained_tasks |= import_finisher.si(self.task_id).set(queue='concurrent')
-        final_task = chained_tasks.apply_async()
+
+        final_task = chained_tasks.apply_async(queue='concurrent')
         return final_task
 
     def is_importable_file(self, file_name):
@@ -507,10 +511,7 @@ def import_resource(self, resource, username, owner_type, owner):
     # pylint: disable=too-many-arguments
     @staticmethod
     def import_concept_map(owner, owner_type, resource, resource_type, url, username):
-        source = Source.objects.filter(canonical_url=url)
-        if not source:
-            url = IdentifierSerializer.convert_fhir_url_to_ocl_uri(url, 'sources')
-            source = Source.objects.filter(uri=url)
+        source = ResourceImporter.find_existing_source(owner, owner_type, url)
         context = {
             'request': ImportRequest(owner_type, owner, username, resource_type)
         }
@@ -524,13 +525,52 @@ def import_concept_map(owner, owner_type, resource, resource_type, url, username
             serializer.save()
         return serializer.errors if serializer.errors else result
 
+    @staticmethod
+    def find_existing_source(owner, owner_type, url):
+        org, user = None, None
+        if owner_type.lower() in ['orgs', 'organization']:
+            org = Organization.objects.filter(mnemonic=owner).first()
+        else:
+            user = UserProfile.objects.filter(username=owner).first()
+
+        if not org and not user:
+            raise ValidationError(f"Cannot find owner of type {owner_type} and id {owner}")
+
+        if org:
+            source = Source.objects.filter(canonical_url=url, organization=org)
+        else:
+            source = Source.objects.filter(canonical_url=url, user=user)
+        if not source:
+            url = IdentifierSerializer.convert_fhir_url_to_ocl_uri(url, 'sources')
+            if org:
+                source = Source.objects.filter(uri=url, organization=org)
+            else:
+                source = Source.objects.filter(uri=url, user=user)
+        return source
+
     # pylint: disable=too-many-arguments
     @staticmethod
     def import_value_set(owner, owner_type, resource, resource_type, url, username):
-        collection = Collection.objects.filter(canonical_url=url)
+        org, user = None, None
+        if owner_type.lower() in ['orgs', 'organization']:
+            org = Organization.objects.filter(mnemonic=owner).first()
+        else:
+            user = UserProfile.objects.filter(username=owner).first()
+
+        if not org and not user:
+            raise ValidationError(f"Cannot find owner of type {owner_type} and id {owner}")
+
+        if org:
+            collection = Collection.objects.filter(canonical_url=url, organization=org)
+        else:
+            collection = Collection.objects.filter(canonical_url=url, user=user)
+
         if not collection:
             url = IdentifierSerializer.convert_fhir_url_to_ocl_uri(url, 'collections')
-            collection = Collection.objects.filter(uri=url)
+            if org:
+                collection = Collection.objects.filter(uri=url, organization=org)
+            else:
+                collection = Collection.objects.filter(uri=url, user=user)
         context = {
             'request': ImportRequest(owner_type, owner, username, resource_type)
         }
@@ -547,10 +587,7 @@ def import_value_set(owner, owner_type, resource, resource_type, url, username):
     # pylint: disable=too-many-arguments
     @staticmethod
     def import_code_system(owner, owner_type, resource, resource_type, url, username):
-        source = Source.objects.filter(canonical_url=url)
-        if not source:
-            url = IdentifierSerializer.convert_fhir_url_to_ocl_uri(url, 'sources')
-            source = Source.objects.filter(uri=url)
+        source = ResourceImporter.find_existing_source(owner, owner_type, url)
         context = {
             'request': ImportRequest(owner_type, owner, username, resource_type)
         }
diff --git a/core/value_sets/serializers.py b/core/value_sets/serializers.py
index 25f02d3a..8eff2c34 100644
--- a/core/value_sets/serializers.py
+++ b/core/value_sets/serializers.py
@@ -202,7 +202,7 @@ def update(self, instance, validated_data):
         head_collection = instance.head
         new_version = validated_data.get('version')
 
-        if instance.version == new_version:
+        if instance.active_versions.filter(version=new_version):
             self._errors.update({'version': f'Version {new_version} already exists for CodeSystem'
                                             f' {instance.mnemonic}.'})
             return instance