Can you try to open that url and see what happens?
https://downloads.getmonero.org/gui/monero-gui-linux-x64-v0.18.3.3.tar.bz2
This is basically what the container tries to download, is there a file called: monero-gui_v0.18.3.3.tar.bz2 in the main directory from the container? If there is a file called monero-gui_v0.18.3.3.tar.bz2 try to delete it, restart the container and see what happens.
Please let me know if that fixes the issue so that I can modify the container so that doesn't happen again.