User blog comment:Brianbreed/The Biggest Single Plot Hole in Mass Effect 2/@comment-2055627-20110911153522

There's not much to think about. The collector base was about to explode and they needed to get out of the system to avoid it, just a short jump between star systems would suffice. Once they were sure the danger was gone they go back to the relay in the Tartarus Debris Field (which there must be one otherwise how do the collectors leave their own base to kidnap colonies?).

As for the bug, well Cerberus has been studying the collectors maybe one was found on Freedom's Progress or Veetor caught one.