Did reinstall PHP7.0-FPM by: apt-get --purge remove php7.0-fpm and apt-get install php7.0-fpm but I still experience the same error.
I mean it cannot be a solution to simply deactivate QUIC, there must be a way to use proper logins from popular open source webapps over QUIC with Caddy… Even GOOGLE sites served over QUIC are usable for logins.