diff --git a/ESSArch_Core/WorkflowEngine/signals.py b/ESSArch_Core/WorkflowEngine/signals.py
index 5ecf0ad9d..b50eb0884 100644
--- a/ESSArch_Core/WorkflowEngine/signals.py
+++ b/ESSArch_Core/WorkflowEngine/signals.py
@@ -4,6 +4,7 @@
 from django.db.models.signals import post_save, pre_save
 from django.dispatch import receiver
 
+from ESSArch_Core.db.utils import check_db_connection
 from ESSArch_Core.WorkflowEngine.models import ProcessStep, ProcessTask
 
 
@@ -31,6 +32,7 @@ def step_post_save(sender, instance, created, **kwargs):
 
 @task_received.connect
 def task_received_handler(request=None, **kwargs):
+    check_db_connection()
     logger = logging.getLogger('essarch')
     try:
         t = ProcessTask.objects.get(celery_id=request.task_id)
@@ -39,7 +41,6 @@ def task_received_handler(request=None, **kwargs):
             t.revoke()
     except ProcessTask.DoesNotExist:
         logger.debug('{} signal task_received without ProcessTask'.format(request.task_id))
-        pass
 
 
 @task_revoked.connect
diff --git a/ESSArch_Core/fixity/conversion/backends/base.py b/ESSArch_Core/fixity/conversion/backends/base.py
index 87f45b93e..cf5ccb90f 100644
--- a/ESSArch_Core/fixity/conversion/backends/base.py
+++ b/ESSArch_Core/fixity/conversion/backends/base.py
@@ -6,10 +6,24 @@
 class BaseConverter:
     input_formats = []
     output_formats = []
+    file_converter = True  # Does the validator operate on single files or entire directories?
 
-    def __init__(self, ip=None, user=None):
+    def __init__(self, context=None, include=None, exclude=None, options=None,
+                 data=None, required=True, task=None, ip=None, responsible=None,
+                 stylesheet=None):
+        """
+        Initializes for convert of one or more files
+        """
+        self.context = context
+        self.include = include or []
+        self.exclude = exclude or []
+        self.options = options or {}
+        self.data = data or {}
+        self.required = required
+        self.task = task
         self.ip = ip
-        self.user = user
+        self.responsible = responsible
+        self.stylesheet = stylesheet
 
     @classmethod
     def validate_input_format(cls, fmt):
diff --git a/ESSArch_Core/fixity/models.py b/ESSArch_Core/fixity/models.py
index c6ae17723..2d20b7083 100644
--- a/ESSArch_Core/fixity/models.py
+++ b/ESSArch_Core/fixity/models.py
@@ -121,6 +121,9 @@ def _run_python(self, filepath, rootdir, options, t=None, ip=None, context=None)
             os.chdir(rootdir)
             filepath = normalize_path(filepath)
             cmd = eval(self.prepare_cmd(filepath, options))
+            if isinstance(cmd, str):
+                cmd = (cmd,)
+
             try:
                 [module, task] = self.path.rsplit('.', 1)
                 p = getattr(importlib.import_module(module), task)(task=t, ip=ip, context=context)
diff --git a/ESSArch_Core/fixity/transformation/backends/base.py b/ESSArch_Core/fixity/transformation/backends/base.py
index ba39ffeba..5c9523560 100644
--- a/ESSArch_Core/fixity/transformation/backends/base.py
+++ b/ESSArch_Core/fixity/transformation/backends/base.py
@@ -2,9 +2,24 @@
 
 
 class BaseTransformer:
-    def __init__(self, ip=None, user=None):
+    file_transformer = True  # Does the validator operate on single files or entire directories?
+
+    def __init__(self, context=None, include=None, exclude=None, options=None,
+                 data=None, required=True, task=None, ip=None, responsible=None,
+                 stylesheet=None):
+        """
+        Initializes for transform of one or more files
+        """
+        self.context = context
+        self.include = include or []
+        self.exclude = exclude or []
+        self.options = options or {}
+        self.data = data or {}
+        self.required = required
+        self.task = task
         self.ip = ip
-        self.user = user
+        self.responsible = responsible
+        self.stylesheet = stylesheet
 
     @classmethod
     def transform(cls, path):