Pico CMS can't use ressources stored outside of nexcloud

I recently discovered Pico cms through nextcloud.
I installed the app and started creating a couple of test sites.
Everything works great except that it seems I can’t use ressources (pictures, videos, etc.) stored outside of my nextcloud.
I have installed a Pico CMS outside of nextcloud to test my websites and in that case it works, from pictures to embedded videos, everything works great.
Does anybody has a clue ?