diff --git a/contrib/download_depccg_model.py b/contrib/download_depccg_model.py
index dd3004b0..e84a2110 100644
--- a/contrib/download_depccg_model.py
+++ b/contrib/download_depccg_model.py
@@ -2,7 +2,7 @@
 from urllib.request import urlretrieve
 from depccg.instance_models import MODEL_DIRECTORY
 
-URL = 'https://qnlp.cambridgequantum.com/models/tri_headfirst.tar.gz'
+URL = 'https://qnlp.quantinuum.com/models/tri_headfirst.tar.gz'
 
 print('Please consider using Bobcat, the parser included with lambeq,\n'
       'instead of depccg.')
diff --git a/lambeq/backend/snake_removal.py b/lambeq/backend/snake_removal.py
index 346802ea..d83905f3 100644
--- a/lambeq/backend/snake_removal.py
+++ b/lambeq/backend/snake_removal.py
@@ -30,7 +30,11 @@
 class InterchangerError(Exception):
     """ This is raised when we try to interchange conected boxes. """
     def __init__(self, box0: Box, box1: Box) -> None:
-        super().__init__(f'Boxes {box0} and {box1} do not commute.')
+        super().__init__(box0, box1)
+
+    def __str__(self) -> str:
+        return f'Boxes {self.args[0]} and {self.args[1]} do not commute.'
+
 
 
 def snake_removal(diagram: Diagram, left: bool = False) -> Iterator[Diagram]:
diff --git a/lambeq/text2diagram/ccg_rule.py b/lambeq/text2diagram/ccg_rule.py
index bb62eddb..55261b98 100644
--- a/lambeq/text2diagram/ccg_rule.py
+++ b/lambeq/text2diagram/ccg_rule.py
@@ -27,6 +27,7 @@
 class CCGRuleUseError(Exception):
     """Error raised when a :py:class:`CCGRule` is applied incorrectly."""
     def __init__(self, rule: CCGRule, message: str) -> None:
+        super().__init__(rule, message)
         self.rule = rule
         self.message = message
 
diff --git a/lambeq/text2diagram/ccg_type.py b/lambeq/text2diagram/ccg_type.py
index 1f6b35ef..bf894472 100644
--- a/lambeq/text2diagram/ccg_type.py
+++ b/lambeq/text2diagram/ccg_type.py
@@ -28,6 +28,7 @@ class CCGParseError(Exception):
     """Error when parsing a CCG type string."""
 
     def __init__(self, cat: str, message: str) -> None:
+        super().__init__(cat, message)
         self.cat = cat
         self.message = message
 
diff --git a/lambeq/text2diagram/ccgbank_parser.py b/lambeq/text2diagram/ccgbank_parser.py
index e51f3623..f07336af 100644
--- a/lambeq/text2diagram/ccgbank_parser.py
+++ b/lambeq/text2diagram/ccgbank_parser.py
@@ -58,6 +58,7 @@ def __init__(self, sentence: str = '', message: str = '') -> None:
         else:
             self.sentence = ''
             self.message = sentence
+        super().__init__(sentence, message)
 
     def __str__(self) -> str:
         if self.sentence:
diff --git a/lambeq/text2diagram/depccg_parser.py b/lambeq/text2diagram/depccg_parser.py
index 3d844a7b..8d120c96 100644
--- a/lambeq/text2diagram/depccg_parser.py
+++ b/lambeq/text2diagram/depccg_parser.py
@@ -66,9 +66,10 @@ def _import_depccg() -> None:
 
 class DepCCGParseError(Exception):
     def __init__(self, sentence: str) -> None:
+        super().__init__(sentence)
         self.sentence = sentence
 
-    def __str__(self) -> str:  # pragma: no cover
+    def __str__(self) -> str:
         return f'depccg failed to parse: "{self.sentence!r}".'
 
 
diff --git a/lambeq/text2diagram/model_based_reader/bobcat_parser.py b/lambeq/text2diagram/model_based_reader/bobcat_parser.py
index d4b5f43f..702b7dbd 100644
--- a/lambeq/text2diagram/model_based_reader/bobcat_parser.py
+++ b/lambeq/text2diagram/model_based_reader/bobcat_parser.py
@@ -48,6 +48,7 @@
 
 class BobcatParseError(Exception):
     def __init__(self, sentence: str) -> None:
+        super().__init__(sentence)
         self.sentence = sentence
 
     def __str__(self) -> str:
diff --git a/lambeq/text2diagram/model_based_reader/model_downloader.py b/lambeq/text2diagram/model_based_reader/model_downloader.py
index 44963798..8d1a24b3 100644
--- a/lambeq/text2diagram/model_based_reader/model_downloader.py
+++ b/lambeq/text2diagram/model_based_reader/model_downloader.py
@@ -31,7 +31,7 @@
 from lambeq.core.globals import VerbosityLevel
 from lambeq.typing import StrPathT
 
-MODELS_URL = 'https://qnlp.cambridgequantum.com/models'
+MODELS_URL = 'https://qnlp.quantinuum.com/models'
 MODELS = {'bobcat', 'oncilla'}
 VERSION_FNAME = 'version.txt'
 CHECKSUM_FNAME = 'model_checksum.sha256'
@@ -42,6 +42,7 @@
 
 class ModelDownloaderError(Exception):
     def __init__(self, error_msg: str) -> None:
+        super().__init__(error_msg)
         self.error_msg = error_msg
 
     def __str__(self) -> str:
@@ -87,7 +88,10 @@ def __init__(self,
     def get_url(self) -> str:
         """Get URL for the latest version of specified model."""
 
-        return f'{MODELS_URL}/{self.model}/latest'
+        model_path = self.model
+        if self.model == 'bobcat':
+            model_path = 'bert'
+        return f'{MODELS_URL}/{model_path}/latest'
 
     def get_dir(self,
                 cache_dir: StrPathT | None = None) -> Path:
@@ -125,6 +129,13 @@ def get_local_model_version(self) -> str | None:
         try:
             with open(self.model_dir / VERSION_FNAME) as f:
                 local_version = f.read().strip()
+        except FileNotFoundError:
+            # Fallback: Check for nested directory (e.g. bobcat/bobcat)
+            try:
+                with open(self.model_dir / self.model / VERSION_FNAME) as f:
+                    local_version = f.read().strip()
+            except Exception:
+                local_version = None
         except Exception:
             local_version = None
 
@@ -137,6 +148,14 @@ def download_model(self,
          and then extract the model to `model_dir`"""
 
         if self.remote_version is None:
+            if self.get_local_model_version() is not None:
+                print('Failed to retrieve remote model version. '
+                      'Using local model.', file=sys.stderr)
+                # Check if model is in nested directory and update path
+                nested_dir = self.model_dir / self.model
+                if nested_dir.exists() and (nested_dir / 'config.json').exists():
+                    self.model_dir = nested_dir
+                return
             raise self.version_retrieval_error
 
         expected_checksum = self._get_remote_checksum()
diff --git a/lambeq/text2diagram/model_based_reader/oncilla_parser.py b/lambeq/text2diagram/model_based_reader/oncilla_parser.py
index f15590f3..a516052d 100644
--- a/lambeq/text2diagram/model_based_reader/oncilla_parser.py
+++ b/lambeq/text2diagram/model_based_reader/oncilla_parser.py
@@ -45,6 +45,7 @@
 
 class OncillaParseError(Exception):
     def __init__(self, sentence: str, reason: str = '') -> None:
+        super().__init__(sentence, reason)
         self.sentence = sentence
         self.reason = reason
 
diff --git a/lambeq/text2diagram/pregroup_tree.py b/lambeq/text2diagram/pregroup_tree.py
index 7ed6a9c9..b8780ab2 100644
--- a/lambeq/text2diagram/pregroup_tree.py
+++ b/lambeq/text2diagram/pregroup_tree.py
@@ -24,6 +24,7 @@
 
 class PregroupTreeNodeError(Exception):
     def __init__(self, sentence: str) -> None:
+        super().__init__(sentence)
         self.sentence = sentence
 
     def __str__(self) -> str:
diff --git a/lambeq/text2diagram/web_parser.py b/lambeq/text2diagram/web_parser.py
index ee152464..e2de56c1 100644
--- a/lambeq/text2diagram/web_parser.py
+++ b/lambeq/text2diagram/web_parser.py
@@ -40,10 +40,11 @@
 
 class WebParseError(OSError):
     def __init__(self, sentence: str) -> None:
+        super().__init__(sentence)
         self.sentence = sentence
 
     def __str__(self) -> str:
-        return (f'Web parser could not parse {repr(self.sentence)}')
+        return f'Web parser could not parse {repr(self.sentence)}'
 
 
 class WebParser(CCGParser):
diff --git a/lambeq/training/nelder_mead_optimizer.py b/lambeq/training/nelder_mead_optimizer.py
index 6b2377c0..c2f78eb6 100644
--- a/lambeq/training/nelder_mead_optimizer.py
+++ b/lambeq/training/nelder_mead_optimizer.py
@@ -259,7 +259,7 @@ def objective(self, x: Iterable[Any], y: ArrayLike, w: ArrayLike) -> float:
                 raise ValueError(
                     'Objective function must return a scalar'
                 ) from e
-        return result   # type: ignore[return-value]
+        return result
 
     def backward(self, batch: tuple[Iterable[Any], np.ndarray]) -> float:
         """Calculate the gradients of the loss function.
diff --git a/setup.cfg b/setup.cfg
index edf6f957..c6a8c228 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -75,6 +75,7 @@ extras =
     discopy >= 1.1.7
     jax < 0.6.0
     jaxlib < 0.6.0
+    autoray < 0.6.1
     pennylane >= 0.29.1, < 0.37.0
     pennylane-honeywell
     pennylane-qiskit >= 0.29.1, < 0.37.0