diff --git a/runbot/models/build_error.py b/runbot/models/build_error.py
index a7909333..3bec114b 100644
--- a/runbot/models/build_error.py
+++ b/runbot/models/build_error.py
@@ -298,7 +298,6 @@ class BuildError(models.Model):
         _logger.debug('Merging errors %s', self)
         base_error = self[0]
         base_linked = self[0].parent_id or self[0]
-        old_error_ids = []
         for error in self[1:]:
             assert base_error.fingerprint == error.fingerprint, f'Errors {base_error.id} and {error.id} have a different fingerprint'
             if error.test_tags and not base_linked.test_tags:
@@ -311,8 +310,12 @@ class BuildError(models.Model):
                 error.message_post(body=f'⚠ trying to merge errors with different test-tags from {base_error._get_form_link()} tag: "{base_error.test_tags}"')
                 continue
 
-            base_error.build_ids += error.build_ids
-            error.build_ids = False
+            for build_error_link in error.build_error_link_ids:
+                if build_error_link.build_id not in base_error.build_error_link_ids.build_id:
+                    build_error_link.build_error_id = base_error
+                else:
+                    # as the relation already exists and was not transferred we can remove the old one
+                    build_error_link.unlink()
 
             if error.responsible and not base_linked.responsible:
                 base_error.responsible = error.responsible
@@ -326,7 +329,6 @@ class BuildError(models.Model):
             error.message_post(body=f'Error was merged into {base_linked._get_form_link()}')
             error.child_ids.parent_id = base_error
             error.active = False
-            old_error_ids.append(error.id)
 
     ####################
     #   Actions
@@ -357,7 +359,7 @@ class BuildError(models.Model):
         errors_by_fingerprint = self.env['runbot.build.error'].search([('fingerprint', 'in', list(changed_fingerprints))])
         for fingerprint in changed_fingerprints:
             errors_to_merge = errors_by_fingerprint.filtered(lambda r: r.fingerprint == fingerprint)
-            rec_id = errors_to_merge._merge()
+            errors_to_merge._merge()
 
     def action_assign(self):
         if not any((not record.responsible and not record.team_id and record.file_path and not record.parent_id) for record in self):
diff --git a/runbot/security/ir.model.access.csv b/runbot/security/ir.model.access.csv
index d47dd647..c79b6e97 100644
--- a/runbot/security/ir.model.access.csv
+++ b/runbot/security/ir.model.access.csv
@@ -23,7 +23,7 @@ access_runbot_build_error_user,runbot_build_error_user,runbot.model_runbot_build
 access_runbot_build_error_admin,runbot_build_error_admin,runbot.model_runbot_build_error,runbot.group_runbot_admin,1,1,1,1
 access_runbot_build_error_manager,runbot_build_error_manager,runbot.model_runbot_build_error,runbot.group_runbot_error_manager,1,1,1,1
 access_runbot_build_error_link_user,runbot_runbot_build_error_link_user,runbot.model_runbot_build_error_link,group_user,1,0,0,0
-access_runbot_build_error_link_admin,runbot_runbot_build_error_link_admin,runbot.model_runbot_build_error_link,runbot.group_runbot_admin,1,1,1,0
+access_runbot_build_error_link_admin,runbot_runbot_build_error_link_admin,runbot.model_runbot_build_error_link,runbot.group_runbot_admin,1,1,1,1
 access_runbot_build_error_link_manager,runbot_runbot_build_error_link_manager,runbot.model_runbot_build_error_link,runbot.group_runbot_error_manager,1,1,1,0
 access_runbot_build_error_tag_user,runbot_build_error_tag_user,runbot.model_runbot_build_error_tag,group_user,1,0,0,0
 access_runbot_build_error_tag_admin,runbot_build_error_tag_admin,runbot.model_runbot_build_error_tag,runbot.group_runbot_admin,1,1,1,1
diff --git a/runbot/tests/test_build_error.py b/runbot/tests/test_build_error.py
index 009462fa..a58bbc48 100644
--- a/runbot/tests/test_build_error.py
+++ b/runbot/tests/test_build_error.py
@@ -75,8 +75,11 @@ class TestBuildError(RunbotCase):
         self.assertEqual(len(self.BuildError.search([('fingerprint', '=', error_a.fingerprint)])), 1)
         self.assertTrue(error_a.active, 'The first merged error should stay active')
         self.assertFalse(error_b.active, 'The second merged error should have stay deactivated')
+        self.assertIn(build_a, error_a.build_error_link_ids.build_id)
         self.assertIn(build_a, error_a.build_ids)
+        self.assertIn(build_b, error_a.build_error_link_ids.build_id)
         self.assertIn(build_b, error_a.build_ids)
+        self.assertFalse(error_b.build_error_link_ids)
         self.assertFalse(error_b.build_ids)
 
         error_c = self.BuildError.create({'content': 'foo foo'})
@@ -85,6 +88,15 @@ class TestBuildError(RunbotCase):
         with self.assertRaises(AssertionError):
             (error_a | error_c)._merge()
 
+        # merge two build errors while the build <--> build_error relation already exists
+        error_d = self.BuildError.create({'content': 'foo bar'})
+        self.BuildErrorLink.create({'build_id': build_a.id, 'build_error_id': error_d.id})
+        (error_a | error_d)._merge()
+        self.assertIn(build_a, error_a.build_error_link_ids.build_id)
+        self.assertIn(build_a, error_a.build_ids)
+        self.assertFalse(error_d.build_error_link_ids)
+        self.assertFalse(error_d.build_ids)
+
     def test_merge_linked(self):
         top_error = self.BuildError.create({'content': 'foo foo', 'active': False})