diff --git a/packages/models-library/src/models_library/clusters.py b/packages/models-library/src/models_library/clusters.py
index 8b38913c2466..c857073deadf 100644
--- a/packages/models-library/src/models_library/clusters.py
+++ b/packages/models-library/src/models_library/clusters.py
@@ -1,8 +1,7 @@
 from enum import auto
 from pathlib import Path
-from typing import Final, Literal, TypeAlias
+from typing import Final, Literal, Self, TypeAlias
 
-from models_library.utils._original_fastapi_encoders import jsonable_encoder
 from pydantic import (
     AnyUrl,
     BaseModel,
@@ -222,29 +221,23 @@ class Cluster(BaseCluster):
         },
     )
 
-    @model_validator(mode="before")
-    @classmethod
-    def check_owner_has_access_rights(cls, values):
-        values = jsonable_encoder(values)
-
-        is_default_cluster = bool(values["id"] == DEFAULT_CLUSTER_ID)
-        owner_gid = values["owner"]
+    @model_validator(mode="after")
+    def check_owner_has_access_rights(self: Self) -> Self:
+        is_default_cluster = bool(self.id == DEFAULT_CLUSTER_ID)
+        owner_gid = self.owner
 
         # check owner is in the access rights, if not add it
-        access_rights = values.get("access_rights", values.get("accessRights", {}))
+        access_rights = self.access_rights.copy()
         if owner_gid not in access_rights:
             access_rights[owner_gid] = (
-                CLUSTER_USER_RIGHTS.model_dump()
-                if is_default_cluster
-                else CLUSTER_ADMIN_RIGHTS.model_dump()
+                CLUSTER_USER_RIGHTS if is_default_cluster else CLUSTER_ADMIN_RIGHTS
             )
         # check owner has the expected access
         if access_rights[owner_gid] != (
-            CLUSTER_USER_RIGHTS.model_dump()
-            if is_default_cluster
-            else CLUSTER_ADMIN_RIGHTS.model_dump()
+            CLUSTER_USER_RIGHTS if is_default_cluster else CLUSTER_ADMIN_RIGHTS
         ):
             msg = f"the cluster owner access rights are incorrectly set: {access_rights[owner_gid]}"
             raise ValueError(msg)
-        values["access_rights"] = access_rights
-        return values
+        # NOTE: overcomes frozen configuration (far fetched in ClusterGet model of webserver)
+        object.__setattr__(self, "access_rights", access_rights)
+        return self
diff --git a/services/director-v2/src/simcore_service_director_v2/models/comp_runs.py b/services/director-v2/src/simcore_service_director_v2/models/comp_runs.py
index 2c671d2c146c..aba02269415e 100644
--- a/services/director-v2/src/simcore_service_director_v2/models/comp_runs.py
+++ b/services/director-v2/src/simcore_service_director_v2/models/comp_runs.py
@@ -95,8 +95,10 @@ def convert_null_to_empty_metadata(cls, v):
                     "cluster_id": 0,
                     "iteration": 42,
                     "result": "UNKNOWN",
-                    "created": "2021-03-01 13:07:34.19161",
-                    "modified": "2021-03-01 13:07:34.19161",
+                    "started": None,
+                    "ended": None,
+                    "created": "2021-03-01T13:07:34.191610",
+                    "modified": "2021-03-01T13:07:34.191610",
                     "cancelled": None,
                     "use_on_demand_clusters": False,
                 },
@@ -107,8 +109,10 @@ def convert_null_to_empty_metadata(cls, v):
                     "cluster_id": None,  # this default to DEFAULT_CLUSTER_ID
                     "iteration": 42,
                     "result": "NOT_STARTED",
-                    "created": "2021-03-01 13:07:34.19161",
-                    "modified": "2021-03-01 13:07:34.19161",
+                    "started": None,
+                    "ended": None,
+                    "created": "2021-03-01T13:07:34.191610",
+                    "modified": "2021-03-01T13:07:34.191610",
                     "cancelled": None,
                     "use_on_demand_clusters": False,
                 },
@@ -119,10 +123,10 @@ def convert_null_to_empty_metadata(cls, v):
                     "cluster_id": 123,
                     "iteration": 12,
                     "result": "SUCCESS",
-                    "created": "2021-03-01 13:07:34.19161",
-                    "modified": "2021-03-01 13:07:34.19161",
-                    "started": "2021-03-01 08:07:34.19161",
-                    "ended": "2021-03-01 13:07:34.10",
+                    "created": "2021-03-01T13:07:34.191610",
+                    "modified": "2021-03-01T13:07:34.191610",
+                    "started": "2021-03-01T08:07:34.191610",
+                    "ended": "2021-03-01T13:07:34.10",
                     "cancelled": None,
                     "metadata": {
                         "node_id_names_map": {},
@@ -140,10 +144,10 @@ def convert_null_to_empty_metadata(cls, v):
                     "cluster_id": 123,
                     "iteration": 12,
                     "result": "SUCCESS",
-                    "created": "2021-03-01 13:07:34.19161",
-                    "modified": "2021-03-01 13:07:34.19161",
-                    "started": "2021-03-01 8:07:34.19161",
-                    "ended": "2021-03-01 13:07:34.10",
+                    "created": "2021-03-01T13:07:34.191610",
+                    "modified": "2021-03-01T13:07:34.191610",
+                    "started": "2021-03-01T08:07:34.191610",
+                    "ended": "2021-03-01T13:07:34.10",
                     "cancelled": None,
                     "metadata": None,
                     "use_on_demand_clusters": False,