diff --git a/vdirsyncer/http.py b/vdirsyncer/http.py
index 30cfe909..3a158862 100644
--- a/vdirsyncer/http.py
+++ b/vdirsyncer/http.py
@@ -147,7 +147,12 @@ async def request(
 
     logger.debug(response.status)
     logger.debug(response.headers)
-    logger.debug(response.content)
+    if (
+        response.status >= 400
+        and hasattr(response, "content")
+        and hasattr(response.content, "_buffer")
+    ):
+        logger.debug(response.content._buffer)
 
     if response.status == 412:
         raise exceptions.PreconditionFailed(response.reason)
diff --git a/vdirsyncer/storage/dav.py b/vdirsyncer/storage/dav.py
index dcaf15e9..9726b10f 100644
--- a/vdirsyncer/storage/dav.py
+++ b/vdirsyncer/storage/dav.py
@@ -553,7 +553,7 @@ async def get_multi(self, hrefs):
                 else:
                     rv.append((href, Item(raw), etag))
             for href in hrefs_left:
-                raise exceptions.NotFoundError(href)
+                dav_logger.warning(f"Skipping {href}, not found")
 
             for href, item, etag in rv:
                 yield href, item, etag
@@ -593,12 +593,52 @@ async def _put(self, href, item, etag):
     async def update(self, href, item, etag):
         if etag is None:
             raise ValueError("etag must be given and must not be None.")
-        href, etag = await self._put(self._normalize_href(href), item, etag)
+        try:
+            href, etag = await self._put(self._normalize_href(href), item, etag)
+        except aiohttp.ClientResponseError as e:
+            if e.status == 409:
+                dav_logger.debug("Conflict, will delete old event and recreate it.")
+                try:
+                    await self.delete(self._normalize_href(href), None)
+                    dav_logger.debug("Now trying again")
+                    rv = await self._put(self._normalize_href(href), item, None)
+                except aiohttp.ClientResponseError as delerr:
+                    dav_logger.debug(f"delerr.status = {delerr.status}")
+                    if delerr.status == 403 or delerr.status == 404:
+                        dav_logger.warning("Old event not found, ignoring")
+                        rv = None, None
+                    else:
+                        raise
+            elif e.status == 403:
+                dav_logger.debug("Google Calendar refusing update, ignore")
+                rv = None, None
+            else:
+                raise
         return etag
 
     async def upload(self, item: Item):
         href = self._get_href(item)
-        rv = await self._put(href, item, None)
+        try:
+            rv = await self._put(href, item, None)
+        except aiohttp.ClientResponseError as e:
+            if e.status == 409:
+                dav_logger.debug("Conflict, will delete old event and recreate it.")
+                try:
+                    await self.delete(href, None)
+                    dav_logger.debug("Now trying again")
+                    rv = await self._put(href, item, None)
+                except aiohttp.ClientResponseError as delerr:
+                    dav_logger.debug(f"delerr.status = {delerr.status}")
+                    if delerr.status == 403 or delerr.status == 404:
+                        dav_logger.warning("Old event not found, ignoring")
+                        rv = None, None
+                    else:
+                        raise
+            elif e.status == 403:
+                dav_logger.debug("Google Calendar refusing update, ignore")
+                rv = None, None
+            else:
+                raise
         return rv
 
     async def delete(self, href, etag):
@@ -633,6 +673,7 @@ def _parse_prop_responses(self, root, handled_hrefs=None):
             props = response.findall("{DAV:}propstat/{DAV:}prop")
             if props is None or not len(props):
                 dav_logger.debug(f"Skipping {href!r}, properties are missing.")
+                dav_logger.debug(f"Response for {href!r}: {etree.tostring(response)}")
                 continue
             else:
                 props = _merge_xml(props)
diff --git a/vdirsyncer/sync/__init__.py b/vdirsyncer/sync/__init__.py
index 8678bc9a..6e489dae 100644
--- a/vdirsyncer/sync/__init__.py
+++ b/vdirsyncer/sync/__init__.py
@@ -208,7 +208,6 @@ async def _run_impl(self, a, b):
                 )
             )
             href, etag = await self.dest.storage.upload(self.item)
-            assert href is not None
 
         self.dest.status.insert_ident(
             self.ident, ItemMetadata(href=href, hash=self.item.hash, etag=etag)