Change username of LDAP-only-user invalidates session

I have a setup where the realm has a LDAP user federation. The users are not imported so there is no local user representation stored in KeyCloak.

Changing the username in the account form works. But when I refresh the page, the session seems to get invalid and the login page is shown.

Is that a known issue or have I made something wrong?

Thanks in advance
Claus