diff --git a/radicale/storage.py b/radicale/storage.py
index 5a63434..016afb6 100644
--- a/radicale/storage.py
+++ b/radicale/storage.py
@@ -227,7 +227,12 @@ class Collection:
 
     def list(self):
         """List collection items."""
-        for href in os.listdir(self._filesystem_path):
+        try:
+            hrefs = os.listdir(self._filesystem_path)
+        except IOError:
+            return
+
+        for href in hrefs:
             path = os.path.join(self._filesystem_path, href)
             if not href.endswith(".props") and os.path.isfile(path):
                 with open(path, encoding=STORAGE_ENCODING) as fd:
@@ -348,8 +353,13 @@ class Collection:
         if os.path.exists(props_path):
             with open(props_path, encoding=STORAGE_ENCODING) as prop_file:
                 properties.update(json.load(prop_file))
-        properties[key] = value
-        with open(props_path, "w", encoding=STORAGE_ENCODING) as prop_file:
+
+        if value:
+            properties[key] = value
+        else:
+            properties.pop(key, None)
+
+        with open(props_path, "w+", encoding=STORAGE_ENCODING) as prop_file:
             json.dump(properties, prop_file)
 
     @property
diff --git a/radicale/xmlutils.py b/radicale/xmlutils.py
index 2e09993..81d6f28 100644
--- a/radicale/xmlutils.py
+++ b/radicale/xmlutils.py
@@ -442,19 +442,13 @@ def proppatch(path, xml_request, collection):
     href.text = _href(path)
     response.append(href)
 
-    with collection.props as collection_props:
-        for short_name, value in props_to_set.items():
-            if short_name.split(":")[-1] == "calendar-timezone":
-                collection.replace(None, value)
-            collection_props[short_name] = value
-            _add_propstat_to(response, short_name, 200)
-        for short_name in props_to_remove:
-            try:
-                del collection_props[short_name]
-            except KeyError:
-                _add_propstat_to(response, short_name, 412)
-            else:
-                _add_propstat_to(response, short_name, 200)
+    for short_name, value in props_to_set.items():
+        collection.set_meta(short_name, value)
+        _add_propstat_to(response, short_name, 200)
+
+    for short_name in props_to_remove:
+        collection.set_meta(short_name, '')
+        _add_propstat_to(response, short_name, 200)
 
     return _pretty_xml(multistatus)
 
@@ -522,13 +516,14 @@ def report(path, xml_request, collection):
         if name:
             # Reference is an item
             path = "/".join(hreference.split("/")[:-1]) + "/"
-            try:
-                items = [collection.get(name)]
-            except KeyError:
+            item = collection.get(name)
+            if item is None:
                 multistatus.append(
                     _item_response(hreference, found_item=False))
                 continue
 
+            items = [item]
+
         else:
             # Reference is a collection
             path = hreference