lftp silently refuses to download certain directories, files

I am using the following command:

lftp -c 'user user password ; set xfer:clobber off; set net:max-retries 0; set net:persist-retries 0; mirror --parallel=500 --verbose=10 --only-missing --ignore-time --loop https://remote.tld repo/; exit'

However, once LFTP is done, it fails to mirror some directories as I manually noticed while trying to access something present on the remote web server, but not on my side. No errors were produced. Why is this happening? Are there any alternatives?