* Wrong Age -- I originally had a flashback where the main characters met as teenagers, but something just wasn't working. They felt more like one-dimensional caricatures, and they had an immaturity I didn't want. So, I played around with it. I aged the characters, put them in a different "place" in their lives. It was better, but not "there" yet. So, I aged them again, put them in yet another place in their lives, and now, for some reason, it's working!
* Info Dumps - We all know that too much exposition (background detail) creates more "telling" than showing, which gives the reader a less-active reading experience. I knew that, but wasn't adhering to it. I had ALL this information that the reader just HAD to have the first few paragraphs. Umm, no. I re-read it through fresh eyes, and it came across as this battery of facts, like some sort of list I had to cram into the beginning. All "telling." Ick. So, instead, I re-wrote the section, deciding to sprinkle in the details. What does the reader need to know up front? What could wait a little longer, even a couple of pages' worth? I figured out where to sprinkle in those same bits of background info (none of it changed) in intervals, and now, it feels much more cohesive. And, much more interesting and active.
I think one of the hardest parts about writing/editing is identifying what's working and what's not. As authors, we're so close to our own material, that it's hard to see those things, even when they're right under our noses.
Then, of course, we have to figure out how to fix it. But you can't fix what you can't identify. So it's worth the time and effort to dig in, get your magnifying glass out, put on your Sherlock Holmes cap, and discover what the problem is. Only then can it can be fixable.