Bug? FIEF 0.28.5 - invalid_grant

[ClaudioBsh]

I use fief server and worker within a docker-compose.yml together with traefik (letsencrypt), redis and postgresql.
I start it using "docker-compose up"
I did login to the admin page like e.g.:
https://fiefdemo.mydomain.com/admin
I give my credentials, and press login and see the Admin-Page, see tenant, client etc, fine:-)

I did not change anything! Just call edit on Tenant, but do not do any change.

I close the page and the browser.
I open the browser again, i call:
https://fiefdemo.mydomain.com/admin
I give my credentials and press login and....error... fief-server log is showing "invalid_grant".

I stop all (docker-compose stop, remove networks and volumes), start completly new, try to login to the admin page but get same "invalid_grant" error.

I tried same with "private browser page", but same error.

Any ideas what could be wrong?