Cloning of a public repository asks for authentication

Dear GitLab team,

first of all, thanks for your amazing work with GitLab.

Maybe I'm doing something wrong, but I have some public repositories and GitLab is asking me for authentication when I try to clone them.

This is happening, for example, with XH5For when I run the following command:

$ git clone --recurse-submodules https://gitlab.com/fempar/XH5For.git

How can I avoid mandatory authentication?

Thanks! Víctor