It hasn't worked for a while with me (not sure how long but definitely for the last few versions) but I used it so infrequently that I never bothered to say anything. Plus, I thought it might just be a bug and that when the full 6.4 version came out, it would be fixed. Now that it has come out and there are a lot more downloads nowadays that have incomplete parts (I'm using GigaNews and EasyNews on some things), the Assemble Incompletes is becoming more important. I downgraded to 6.34 in hopes that might do the trick, but nope. I've paused the downloads and tried it, resumed and tried it again, it just doesn't wanna do it anymore.