Issue when Patching null value to ManyToOne attribute with validation

[mgiraud]

API Platform version(s) affected: ^3.4 ^4.2 maybe all versions

Description
Even when setting skip_null_values to false, i've found a weird case where trying to patch null to a ManyToOne value does not work.

I'll do my best to explain my findings. So let's start with this entity

#[ORM\Entity]
#[ORM\Table(name: 'foo')]
#[UniqueEntity(fields: 'name')]
class Foo
{
    #[ORM\Column(name: 'id_foo', type: 'integer')]
    #[Id]
    #[ORM\GeneratedValue(strategy: 'AUTO')]
    private ?int $id = null;

    #[ORM\Column(name: 'name', type: 'text', nullable: false)]
    private ?string $name = null;

    #[ORM\ManyToOne(targetEntity: Bar::class, cascade: ['persist']]
    #[ORM\JoinColumn(name: 'id_bar', referencedColumnName: 'id_bar')]
    private ?Bar $bar = null;

...

Patching a Foo with an existing or a new Bar works fine. But setting it to null does not work.

The deserialized Foo has a null Bar, but during the Validation (after the PRE_VALIDATION and before POST_VALIDATE hooks), during the execution of the UniqueEntityValidator the Foo::$bar is reset to its initial value.
I can reproduce the same issue with a custom validator containing a

$foo = $this->em->getRepository(Foo::class)->findOneByName($value->getName())

I guess it has to do with some doctrine internals like proxy or stuff like that, but i have no proof.
When i have time, i'll make a minimal project.

Possible Solution
I've worked around with a custom validator and a native query.