diff --git a/mdai_utils/download_annotations.py b/mdai_utils/download_annotations.py
index 7ba04d1..820567f 100644
--- a/mdai_utils/download_annotations.py
+++ b/mdai_utils/download_annotations.py
@@ -64,6 +64,8 @@ def get_mask_from_vertices(vertices, upscale_factor=100, original_image_shape=No
     vertices = np.array(vertices).reshape((-1, 2))
     """
     slice_label_mask = get_empty_mask(original_image_shape)
+    if len(vertices) == 0:
+        return slice_label_mask
     slice_shape = slice_label_mask.shape
     apply_supersample = False if upscale_factor is None else upscale_factor > 1
     if not apply_supersample:
@@ -86,13 +88,21 @@ def get_mask_from_vertices(vertices, upscale_factor=100, original_image_shape=No
 
 def get_mask_from_annotation(row, original_image_shape=None, upscale_factor=100):
     annotationMode = row["annotationMode"]
+    rowdata = row.get("data", None)
+    if rowdata is None:
+        return get_empty_mask(original_image_shape)
     if annotationMode == "freeform":
-        vertices = np.array(row["data"]["vertices"]).reshape((-1, 2))
+        rowvertices = rowdata.get("vertices", [])
+        vertices = np.array(rowvertices).reshape((-1, 2))
         slice_label_mask = get_mask_from_vertices(
             vertices, upscale_factor, original_image_shape
         )
     elif annotationMode == "mask":
         slice_label_mask = get_empty_mask(original_image_shape)
+        if rowdata.get("foreground", None) is None:
+            return slice_label_mask
+        if rowdata.get("background", None) is None:
+            return slice_label_mask
         if row.data["foreground"]:
             for i in row.data["foreground"]:
                 slice_label_mask = cv2.fillPoly(
@@ -305,9 +315,10 @@ def merge_slices_into3D(
                     ] = global_annotations_dict["mdai_label_group_ids"]
                 if study_id in global_annotations_dict:
                     # Check for study labels first:
-                    for label in global_annotations_dict[study_id]["study_labels"]:
-                        global_labels_dict.setdefault(label, 0)
-                        global_labels_dict[label] += 1
+                    if "study_labels" in global_annotations_dict[study_id]:
+                        for label in global_annotations_dict[study_id]["study_labels"]:
+                            global_labels_dict.setdefault(label, 0)
+                            global_labels_dict[label] += 1
                     # Check for series labels:
                     if series_id in global_annotations_dict[study_id]:
                         for label in global_annotations_dict[study_id][series_id]:
@@ -497,7 +508,7 @@ def main(args):
         )
 
     # Get the json for annotations
-    last_json_file = get_last_json_file(out_folder, match_str=mdai_project_id)
+    last_json_file = get_last_json_file(out_folder, match_str=mdai_dataset_id)
 
     logger.info(f"Last json file: {last_json_file}")
 
@@ -547,7 +558,13 @@ def main(args):
             hash_path = Path(hash_id.replace(sep, "/") + ".dcm")
             raw_slice_path = Path(match_folder) / hash_path
             pair_data_entry["image"] = str(raw_slice_path.resolve())
-            raw_slice_image = itk.imread(raw_slice_path)
+            try:
+                raw_slice_image = itk.imread(raw_slice_path)
+            except RuntimeError as e:
+                logger.warning(
+                    f"Could not read dicom file: {raw_slice_path}.\n{e}\nIt might be an invalid json data from mdai. Safe to ignore."
+                )
+                continue
 
         for _, row in group.iterrows():
             row_label_id = row["labelId"]
@@ -566,8 +583,6 @@ def main(args):
             # slice_label_mask = np.flipud(slice_label_mask)
             # Use itk to save the mask, even in nifti format
             label_image = itk.image_from_array(slice_label_mask)
-            # We are going to save a 3D slice, we are interested in storing the z-position.
-
             label_name = (
                 mdai_label_ids.inverse.get(row_label_id, False)
                 or row.get("labelName", False)
@@ -598,6 +613,9 @@ def main(args):
 
             itk.imwrite(label_image, str(label_file))
 
+        # Check that pair_data_entry contains at least one label
+        if len(pair_data_entry) < 3:
+            continue
         pair_data.append(pair_data_entry)
 
     with open(pair_data_json_file, "w") as f: