User Logos empty

I miss the Letters in the circle of the user logos.
Not shure that this happens after update to this version. All other works as well.
Even when i add a new user with the name Peter Krause f.e. in the cirkle user logo PK should be seen.
Also the letters are missing at all existing user.

Nextcloud version 25.0.2
Operating system and version Linux 5.18.0-0.deb11.4-amd64 x86_64
Apache or nginx version nginx
PHP version 7.4.26
all running in Docker