I have a download that's 92.09% complete and shows 1 source. It's been sitting there for over a week now not making further progress. So presumably that one source is partial and doesn't have the last 7.91% of the file. Obviously if I'm to get it I need to find another source.
Problem is, for some reason this one won't stay Searching. It reverts to Pending after an hour or two. Manually doing a "find more sources" on it works ... temporarily. Then it reverts again. This doesn't happen for other incomplete downloads with some known sources; just this one and a handful that have over a dozen sources each (all apparently partial, since these too are generally at 90-something percent done and haven't budged in days or even weeks).
IMO, "Searching" shouldn't revert unless one of three things happens: the user does something to stop it (e.g. cancels the download), a novel source is found, or download progress (at least 0.01%) is made -- that is, there is more of the file downloaded than there had been and the percentage-complete indicator shows a strictly larger number than before. Further, "Searching" should be automatic if, say, 7 days pass without at least 0.01% being added to the file's completion status as that long a period without any fresh downloadage worthy of note surely indicates a need for better sources than the currently-known ones.