Failed to load mpv config file

[p3lim]

Running the flatpak version, 0.27.

I've given it extra permissions through flatseal so it can read ~/.config/mpv and ~/.config/celluloid.

These are the logs when I play a video:

Jul 17 16:53:41 desktop dbus-daemon[1403]: [session uid=1000 pid=1403] Activating service name='io.github.celluloid_player.Celluloid' requested by ':1.607' (uid=1000 pid=258039 comm="/usr/bin/nautilus --gapplication-service")
Jul 17 16:53:41 desktop systemd[1370]: Started app-flatpak-io.github.celluloid_player.Celluloid-302888.scope.
Jul 17 16:53:41 desktop dbus-daemon[1403]: [session uid=1000 pid=1403] Successfully activated service 'io.github.celluloid_player.Celluloid'
Jul 17 16:53:41 desktop celluloid[302900]: Failed to update mpv-config-file
Jul 17 16:53:41 desktop gnome-shell[1559]: meta_window_set_stack_position_no_sync: assertion 'window->stack_position >= 0' failed
Jul 17 16:53:42 desktop celluloid[302900]: Failed to open script options directory: /home/p3lim/.var/app/io.github.celluloid_player.Celluloid/config/celluloid/script-opts
Jul 17 16:53:42 desktop celluloid[302900]: Failed to load mpv config file
Jul 17 16:53:42 desktop io.github.celluloid_player.Celluloid[302900]: Cannot load libcuda.so.1

I also tested copying ~/.config/mpv to the ~/.var/.../config directory, didn't make a difference.

Additionally, any setting I set in the GUI doesn't end up anywhere, it doesn't write them to ~/.config/celluloid, nor ~/.var/app/io.github.celluloid_player.Celluloid/config/celluloid, but it somehow remember them. There are some settings stored in dconf, but certainly not all of them.