diff --git a/rhodecode/model/db.py b/rhodecode/model/db.py
--- a/rhodecode/model/db.py
+++ b/rhodecode/model/db.py
@@ -3805,21 +3805,35 @@ class _SetState(object):
         self._pr = pull_request
         self._org_state = back_state or pull_request.pull_request_state
         self._pr_state = pr_state
+        self._current_state = None
 
     def __enter__(self):
         log.debug('StateLock: entering set state context, setting state to: `%s`',
                   self._pr_state)
-        self._pr.pull_request_state = self._pr_state
-        Session().add(self._pr)
-        Session().commit()
+        self.set_pr_state(self._pr_state)
+        return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_val is not None:
+            log.error(traceback.format_exc(exc_tb))
+            return None
+
+        self.set_pr_state(self._org_state)
         log.debug('StateLock: exiting set state context, setting state to: `%s`',
                   self._org_state)
-        self._pr.pull_request_state = self._org_state
-        Session().add(self._pr)
-        Session().commit()
-
+    @property
+    def state(self):
+        return self._current_state
+
+    def set_pr_state(self, pr_state):
+        try:
+            self._pr.pull_request_state = pr_state
+            Session().add(self._pr)
+            Session().commit()
+            self._current_state = pr_state
+        except Exception:
+            log.exception('Failed to set PullRequest %s state to %s', self._pr, pr_state)
+            raise
 
 class _PullRequestBase(BaseModel):
     """
diff --git a/rhodecode/model/pull_request.py b/rhodecode/model/pull_request.py
--- a/rhodecode/model/pull_request.py
+++ b/rhodecode/model/pull_request.py
@@ -507,10 +507,10 @@ class PullRequestModel(BaseModel):
         # operation
         pull_request = PullRequest.get(pull_request.pull_request_id)
 
-        # set as merging, for simulation, and if finished to created so we mark
+        # set as merging, for merge simulation, and if finished to created so we mark
         # simulation is working fine
         with pull_request.set_state(PullRequest.STATE_MERGING,
-                                    final_state=PullRequest.STATE_CREATED):
+                                    final_state=PullRequest.STATE_CREATED) as state_obj:
             MergeCheck.validate(
                 pull_request, auth_user=auth_user, translator=translator)
 
@@ -1099,6 +1099,8 @@ class PullRequestModel(BaseModel):
         if not reviewers_ids:
             return
 
+        log.debug('Notify following reviewers about pull-request %s', reviewers_ids)
+
         pull_request_obj = pull_request
         # get the current participants of this pull request
         recipients = reviewers_ids