diff --git a/odoo/addons/test_new_api/models/test_new_api.py b/odoo/addons/test_new_api/models/test_new_api.py
index 22234f298f3..13485aa9aee 100644
--- a/odoo/addons/test_new_api/models/test_new_api.py
+++ b/odoo/addons/test_new_api/models/test_new_api.py
@@ -149,12 +149,19 @@ class Message(models.Model):
     label = fields.Char(translate=True)
     priority = fields.Integer()
     active = fields.Boolean(default=True)
+    has_important_sibling = fields.Boolean(compute='_compute_has_important_sibling')
 
     attributes = fields.Properties(
         string='Properties',
         definition='discussion.attributes_definition',
     )
 
+    @api.depends('discussion.messages.important')
+    def _compute_has_important_sibling(self):
+        for record in self:
+            siblings = record.discussion.messages - record
+            record.has_important_sibling = any(siblings.mapped('important'))
+
     @api.constrains('author', 'discussion')
     def _check_author(self):
         for message in self.with_context(active_test=False):
diff --git a/odoo/addons/test_new_api/tests/test_onchange.py b/odoo/addons/test_new_api/tests/test_onchange.py
index 50674a434bd..2fdd9ba7c43 100644
--- a/odoo/addons/test_new_api/tests/test_onchange.py
+++ b/odoo/addons/test_new_api/tests/test_onchange.py
@@ -1236,3 +1236,19 @@ class TestComputeOnchange2(common.TransactionCase):
         )
         with Form(record) as form:
             form.precision_rounding = 0.0001
+
+    def test_new_one2many_on_existing_record(self):
+        discussion = self.env['test_new_api.discussion'].create({
+            'messages': [Command.create({'body': 'Required Body', 'important': True})],
+            'name': 'Required field',
+            'participants': [Command.set(self.env.user.ids)],
+        })
+
+        with Form(discussion, 'test_new_api.discussion_form_2') as discussion_form:
+            self.assertEqual(len(discussion_form.messages), 1)
+            with discussion_form.messages.new() as message_form:
+                # this actually checks that during the onchange, the new message
+                # has access to its sibling messages through the discussion
+                self.assertEqual(message_form.has_important_sibling, True)
+                message_form.body = 'Required Body'
+            self.assertEqual(len(discussion_form.messages), 2)
diff --git a/odoo/addons/test_new_api/tests/test_views.py b/odoo/addons/test_new_api/tests/test_views.py
index 51cb4705bb9..f45258700ef 100644
--- a/odoo/addons/test_new_api/tests/test_views.py
+++ b/odoo/addons/test_new_api/tests/test_views.py
@@ -10,7 +10,7 @@ class TestDefaultView(common.TransactionCase):
     def test_default_form_view(self):
         self.assertEqual(
             etree.tostring(self.env['test_new_api.message']._get_default_form_view()),
-            b'<form><sheet string="Test New API Message"><group><group><field name="discussion"/></group></group><group><field name="body"/></group><group><group><field name="author"/><field name="display_name"/><field name="double_size"/><field name="author_partner"/><field name="label"/><field name="active"/></group><group><field name="name"/><field name="size"/><field name="discussion_name"/><field name="important"/><field name="priority"/><field name="attributes"/></group></group><group><separator/></group></sheet></form>'
+            b'<form><sheet string="Test New API Message"><group><group><field name="discussion"/></group></group><group><field name="body"/></group><group><group><field name="author"/><field name="display_name"/><field name="double_size"/><field name="author_partner"/><field name="label"/><field name="active"/><field name="attributes"/></group><group><field name="name"/><field name="size"/><field name="discussion_name"/><field name="important"/><field name="priority"/><field name="has_important_sibling"/></group></group><group><separator/></group></sheet></form>'
         )
         self.assertEqual(
             etree.tostring(self.env['test_new_api.creativework.edition']._get_default_form_view()),
diff --git a/odoo/addons/test_new_api/views/test_new_api_views.xml b/odoo/addons/test_new_api/views/test_new_api_views.xml
index 88d45351ce5..2acac075393 100644
--- a/odoo/addons/test_new_api/views/test_new_api_views.xml
+++ b/odoo/addons/test_new_api/views/test_new_api_views.xml
@@ -128,6 +128,7 @@
                                         <field name="author"/>
                                         <field name="body" required="1"/>
                                         <field name="size"/>
+                                        <field name="has_important_sibling"/>
                                     </tree>
                                 </field>
                             </page>
diff --git a/odoo/fields.py b/odoo/fields.py
index 20e97e5b0f6..51b0ab805e6 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -1450,7 +1450,6 @@ class Integer(Field):
         return value
 
     def _update(self, records, value):
-        # special case, when an integer field is used as inverse for a one2many
         cache = records.env.cache
         for record in records:
             cache.set(record, self, value.id or 0)
@@ -4154,9 +4153,8 @@ class _RelationalMulti(_Relational):
         if value:
             cache = records.env.cache
             for record in records:
-                if cache.contains(record, self):
-                    val = self.convert_to_cache(record[self.name] | value, record, validate=False)
-                    cache.set(record, self, val)
+                val = self.convert_to_cache(record[self.name] | value, record, validate=False)
+                cache.set(record, self, val)
             records.modified([self.name])
 
     def convert_to_cache(self, value, record, validate=True):
diff --git a/odoo/models.py b/odoo/models.py
index 944028f929b..4b39e7554b0 100644
--- a/odoo/models.py
+++ b/odoo/models.py
@@ -5973,7 +5973,7 @@ class BaseModel(metaclass=MetaModel):
         cache = self.env.cache
         fields = self._fields
         try:
-            field_values = [(fields[name], value) for name, value in values.items()]
+            field_values = [(fields[name], value) for name, value in values.items() if name != 'id']
         except KeyError as e:
             raise ValueError("Invalid field %r on model %r" % (e.args[0], self._name))
 
@@ -5987,17 +5987,10 @@ class BaseModel(metaclass=MetaModel):
                 inv_recs = self[field.name].filtered(lambda r: not r.id)
                 if not inv_recs:
                     continue
+                # we need to adapt the value of the inverse fields to integrate self into it:
+                # x2many fields should add self, while many2one fields should replace with self
                 for invf in self.pool.field_inverses[field]:
-                    # DLE P98: `test_40_new_fields`
-                    # /home/dle/src/odoo/master-nochange-fp/odoo/addons/test_new_api/tests/test_new_fields.py
-                    # Be careful to not break `test_onchange_taxes_1`, `test_onchange_taxes_2`, `test_onchange_taxes_3`
-                    # If you attempt to find a better solution
-                    for inv_rec in inv_recs:
-                        if not cache.contains(inv_rec, invf):
-                            val = invf.convert_to_cache(self, inv_rec, validate=False)
-                            cache.set(inv_rec, invf, val)
-                        else:
-                            invf._update(inv_rec, self)
+                    invf._update(inv_recs, self)
 
     def _convert_to_record(self, values):
         """ Convert the ``values`` dictionary from the cache format to the