The "need more sources" would just be unlucky choices for downloads or else the persons who had the files when you originally downloaded them are presently not online.
Search results probably remain on the network for a minimum 30 minutes after someone has left, so sometimes you choose a file to download and the person is actually no longer online. Else, the person has upload slots set to zero and some people do do this unfortunately. And some clear their shares during their sessions online or at the end of their session.

As for the connection file, it is not perfect. I've been using my own custom approach for it for better or worse. But note that I have been updating them on a regular basis up to now. I have been trying to avoid adding hosts that regularly change their host address.

I am still very much in 'learning' mode about how BS connects. I have a suspicion the program may also use the 'hosts-state' log when connecting. This file gives details about which hosts the program was last connected to. If this is the case, I may add a customized 'hosts-state' log file to the installer also. I will need to test if this is actually the case. I have a suspicion if the log file has hosts not listed in the connection file, BS may panic a little.

If anybody has advice, please feel free.