diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3d808e7f..4acca083 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,13 +10,16 @@ Keep it human-readable, your future self will thank you!
 
 ## [Unreleased](https://github.com/ecmwf/anemoi-datasets/compare/0.5.8...HEAD)
 
+## Changed
+
+- Fix metadata serialization handling of numpy.integer (#140)
+- Fix cutout slicing of grid dimension (#145)
 
 ### Added
 
 - Call filters from anemoi-transform
 - make test optional when adls is not installed Pull request #110
 
-
 ## [0.5.8](https://github.com/ecmwf/anemoi-datasets/compare/0.5.7...0.5.8) - 2024-10-26
 
 ### Changed
diff --git a/src/anemoi/datasets/data/dataset.py b/src/anemoi/datasets/data/dataset.py
index 8ab06757..185cf297 100644
--- a/src/anemoi/datasets/data/dataset.py
+++ b/src/anemoi/datasets/data/dataset.py
@@ -15,6 +15,7 @@
 import warnings
 from functools import cached_property
 
+import numpy as np
 from anemoi.utils.dates import frequency_to_seconds
 from anemoi.utils.dates import frequency_to_string
 from anemoi.utils.dates import frequency_to_timedelta
@@ -42,6 +43,9 @@ def _tidy(v):
     if isinstance(v, slice):
         return (v.start, v.stop, v.step)
 
+    if isinstance(v, np.integer):
+        return int(v)
+
     return v
 
 
@@ -241,7 +245,8 @@ def _drop_to_columns(self, vars):
         if not isinstance(vars, (list, tuple, set)):
             vars = [vars]
 
-        assert set(vars) <= set(self.name_to_index)
+        if not set(vars) <= set(self.name_to_index):
+            raise ValueError(f"drop: unknown variables: {set(vars) - set(self.name_to_index)}")
 
         return sorted([v for k, v in self.name_to_index.items() if k not in vars])
 
diff --git a/src/anemoi/datasets/data/grids.py b/src/anemoi/datasets/data/grids.py
index 15915f13..df5ed4b2 100644
--- a/src/anemoi/datasets/data/grids.py
+++ b/src/anemoi/datasets/data/grids.py
@@ -289,14 +289,15 @@ def _get_tuple(self, index):
         """
         index, changes = index_to_slices(index, self.shape)
         # Select data from each LAM
-        lam_data = [lam[index] for lam in self.lams]
+        lam_data = [lam[index[:3]] for lam in self.lams]
 
         # First apply spatial indexing on `self.globe` and then apply the mask
         globe_data_sliced = self.globe[index[:3]]
         globe_data = globe_data_sliced[..., self.global_mask]
 
-        # Concatenate LAM data with global data
-        result = np.concatenate(lam_data + [globe_data], axis=self.axis)
+        # Concatenate LAM data with global data, apply the grid slicing
+        result = np.concatenate(lam_data + [globe_data], axis=self.axis)[..., index[3]]
+
         return apply_index_to_slices_changes(result, changes)
 
     def collect_supporting_arrays(self, collected, *path):
@@ -324,7 +325,8 @@ def shape(self):
         """
         shapes = [np.sum(mask) for mask in self.masks]
         global_shape = np.sum(self.global_mask)
-        return tuple(self.lams[0].shape[:-1] + (sum(shapes) + global_shape,))
+        total_shape = sum(shapes) + global_shape
+        return tuple(self.lams[0].shape[:-1] + (int(total_shape),))
 
     def check_same_resolution(self, d1, d2):
         # Turned off because we are combining different resolutions
diff --git a/src/anemoi/datasets/data/join.py b/src/anemoi/datasets/data/join.py
index 3f97c38a..6b7de3e6 100644
--- a/src/anemoi/datasets/data/join.py
+++ b/src/anemoi/datasets/data/join.py
@@ -124,7 +124,14 @@ def variables_metadata(self):
                 if v in md:
                     result[v] = md[v]
 
-        assert len(result) == len(variables), (result, variables)
+        if len(result) != len(variables):
+            LOG.error("Some variables are missing metadata.")
+            for v in variables:
+                if v not in result:
+                    LOG.error("Missing metadata for %r.", v)
+
+            raise ValueError("Some variables are missing metadata.")
+
         return result
 
     @cached_property