Curl does not follow symlinks
See, e.g., https://git.geomar.de/data/SLTAC_GLO_PHY_L4_REP/blob/v1.x.x/doc/CMEMS-SL-PUM-008-032-051.pdf which is actually a HTML file detailing the new place.
A replacement for the old instance build runner (old tags dind/docker-in-docker) is available. For details see https://git.geomar.de/open-source/gitlab-docu/-/wikis/build_runner
See, e.g., https://git.geomar.de/data/SLTAC_GLO_PHY_L4_REP/blob/v1.x.x/doc/CMEMS-SL-PUM-008-032-051.pdf which is actually a HTML file detailing the new place.