PHP Apache Docker container: No releases available for package "pecl.php.net/xdebug" in some networks in Ubuntu 18

Question

I`m installing xdebug with pecl in my php/apache docker container:

FROM php:apache-bullseye

RUN pecl install xdebug \
    && docker-php-ext-enable xdebug

This works in my WiFi. But when I plug in my cable, I get error:

No releases available for package "pecl.php.net/xdebug"

Any idea what could cause this? Could this be an Ubuntu problem? I`m using Ubuntu 18. The workaround to switch network is easy. But this can`t be a solution.