diff --git a/arcade/texture_atlas/atlas_default.py b/arcade/texture_atlas/atlas_default.py
index a82170247..18c79ead2 100644
--- a/arcade/texture_atlas/atlas_default.py
+++ b/arcade/texture_atlas/atlas_default.py
@@ -240,10 +240,19 @@ def unique_textures(self) -> list[Texture]:
         """
         # Grab the first texture from each set
         textures: list[Texture] = []
-        for tex_set in self._unique_textures.values():
+        # NOTE: keys can drop out of the dict during iteration.
+        #       Copy they keys and look up each set to avoid this.
+        for key in list(self._unique_textures.keys()):
+            tex_set = self._unique_textures.get(key, None)
+            # Entry was GCed during iteration
+            if tex_set is None:
+                continue
+            # Corrupt data
             if len(tex_set) == 0:
                 raise RuntimeError("Empty set in unique textures")
+
             textures.append(next(iter(tex_set)))
+
         return textures
 
     @property
@@ -300,7 +309,12 @@ def _add(self, texture: Texture, create_finalizer=True) -> tuple[int, AtlasRegio
                 self.write_image(texture.image_data.image, x, y)
             except AllocatorException:
                 if not self._auto_resize:
-                    raise
+                    raise AllocatorException(
+                        f"No more space for image {texture.image_data.hash} "
+                        f"size={texture.image.size}. "
+                        f"Curr size: {self._size}. "
+                        f"Max size: {self._max_size}"
+                    )
 
                 # If we have lost regions/images we can try to rebuild the atlas
                 removed_image_count = self._image_ref_count.get_total_decref()