He said earlier on that he'd tried disconnecting overnight and it still leaked, but I wouldn't rule it out yet.
There's only so many places it can be leaking from. If you really want to find it then make up another soap solution, check that it is actually good for blowing bubbles, and make sure to give everything a good spray with it. Fill with water and pressurise to >20psi.
At this point though I'd probably just ignore it and brew anyway rather than spending time on it. If it doesn't impact your brew then who cares.