backend: Fix handling of invalid stop byte error

backend/monsun_backend/command_execution.py

@@ -256,6 +256,10 @@ class CommandBytesReadInsufficient(CommandInterpretationError):
     """Raised in case the command could not be interpreted"""
 
 
+class InvalidStopByteError(CommandInterpretationError):
+    """Raised in case of an invalid stop byte."""
+
+
 class CommandInterpreter:
     header_size = 4
 
@@ -312,7 +316,7 @@ class CommandInterpreter:
 
         if stop_byte != 0xFF:
             self._logger.error("Invalid stop byte")
-            raise CommandInterpretationError()
+            raise InvalidStopByteError()
 
         try:
             return bytes_read[self.header_size + self.data_length + 1 :]
@@ -354,8 +358,11 @@ class SerialReceiver:
                         bytes_read=self._bytes_unread,
                     ),
                 )
-            # except CommandBytesReadInsufficient:
-            #     return commands_received, responses_received
+            except InvalidStopByteError:
+                # drop bytes until after the next stop byte or buffer is empty
+                while self._bytes_unread:
+                    if self._bytes_unread.pop(0) == 0xFF:
+                        continue
             except CommandInterpretationError:
                 return commands_received, responses_received