One thing to try might be to right-click the file & use the pause function for 10 seconds or so, then unpause.
I think I understand more of your problem now after re-reading. By finishing, do you mean they have already reached 100% but are rechecking the hash to be sure all is ok before reaching the completed status?
If that is the case, the files themselves might be fine, just LW is having problems with the recheck process. I've heard of this issue before.