I've written several times about finding a problem when you're not looking right at it. Sometimes looking around the problem means looking at a different time. Of course we'd all like to find all the problems immediately, but it isn't going to happen. So let it rest, and when you get through what you're working on, well that's when you go looking for the subtle problems.
You find a thread, and you pull it.
In the midst of a release, those niggling little things that aren't quite problems show up. These are the things that are weird but not wrong. So it took a little longer for the upgrader to run, but hey, it completed. Okay, that's plausible. And it's not wrong, per se. But be sure to write it down.
Between releases you'd better come back to those things that were weird. A lot of the time they're just normal things - hey, your upgrader ran slow because you happened to run it on a machine with a slow disk drive. No problem. Sometimes, though, you pull that thread and you find a real deep subtle problem.
So take a deep breath.... and pull.