Language override in SignIn User Flow

Question

I'm trying to override certain (error) messages in my SignIn User Flow in Entra External ID and it looks like language override is the only way for me to do that. I have two issues while doing that.

1. After re-uploading the override JSON some values get replaced correctly and some don't. For example:

The top "SignIn_Description" gets replaced correctly but the error override and all the other error overrides don't work for me. I still see the old text in the SignIn User Flow. In this case the default for german "SignIn_EmailAccountNotFound_Error" is "Kein Konto mit dieser E-Mail-Adresse gefunden."

This is the default in the override file before editing it:

This is the default that gets shown no matter what i put into the language override before uploading it:

1. When i download the default override template file and i just re-upload it or i do some changes but i dont replace the {0} in the translation for example in "SignIn_Description" (see below) than it just shows me {0} in the actual sign in flow instead of replacing it with the tenant name (which i assume is what it normally should do and does without any language overrides).

Thank you in advance for the help.