Rename users through Cloud REST API

[SysAdmin]

I create users through the REST API v3.

I understand the displayName parameter is no longer available, as stated in the documentation. That's why I rely on the v1 REST API to update the displayName.

It used to work until the 15th of January, approximately.

Now I get 403 HTTP errors with the following message :

{"key":"forbidden.fieldMutation","context":{"name":{"allowed":false,"reason":{"key":"managedAccount"}}},"errorKey":"forbidden.field-mutation","errorDetail":{"name":{"allowed":false,"reason":{"key":"managedAccount"}}}}

I am able to rename the users manually via the user management menu, as you can see below

Is it possible to rename a user account (display name) via api v3 or v2? Have there been any recent changes?

Thank you,