Try this :
sudo apt autoclean -y && sudo apt autoremove -y
sync; echo 3 > /proc/sys/vm/drop_caches && swapoff -a && swapon -a
sudo yunohost tools basic-space-cleanup
And reboot system ?
Then,
yunohost app upgrade piped
Otherwise
upgrade an existing install:
sudo yunohost app upgrade piped -u https://github.com/YunoHost-Apps/piped_ynh/tree/testing