As a consultant, I get called into projects in varying states of disarray. Most of the time, things aren't nearly as bad as they appear. As a sweeping generalization, there are only couple of a main issues that I encounter that repeat themselves to cause the downward spiral.
Chief among these issues is Fear. Fear of the unknown, fear of change, fear of failure. It manifests itself by an increase in artificial controls. More status reporting, more censorship, less proactive vocalizations, more questions, less answers. When the fear-response is high, accountability becomes cloudy and nebulous. The answers become subjective and verbose. Sometimes people shift to formality and process, others simply clam-up and stop interacting.
One tried and true technique to handling fear is using Information. Clear and obvious transparency generates trust, removes ignorance, reduces fear. When you encounter people showing a high fear-response, shower them with information. Be transparent, open, and forthcoming. The more people are aware of their situation, can validate their own perceptions with your clear words, the higher the trust for the unknown. If you don't know something, tell them. But make sure you tell them what you do know. Share anything and everything you possibly can so that they can construct their own reality using that information. The richer the detail, the less fear. The more they participate in the process, by way of sharing in the information flow, the more empowered they will feel about the process, the situation.
Another key issue is Churn. When a problem area arises, good people will try and handle it. Once it becomes obvious that an issue is no longer just a simple problem, but a symptom of a larger issue, they tend to move on. If you realize the rock you are trying to move is really a part of the mountain, you will think twice about your choice of rocks. Sometimes we'll simply give up, other times we might choose a different rock. It is pretty rare that someone will be willing to wear themselves down fighting to move a mountain that was supposed to be a rock. The process of bringing in people to beat on the rock, who figure out it is not just a rock, give up, leave, and must be replaced, is called Churn. In these situations, there can be a tendency to fault the various parties brought in to confront the rock. After all, they were not able to move the rock, so they have failed, right? If it is just once or twice, perhaps that would be an acceptable conclusion. But once you've repeated this process a few times, you might need to examine the large situation. The common denominator in those cases is the person trying to move the rock, who is unwilling to acknowledge the mountain. They repeatedly insist on throwing people at the rock, watching them bloody themselves and shaming them for failure. All the while acting as instigators of the vicious cycle.
The hardest part of addressing churn is identifying when it occurs. Sometimes only experience and objectivity can provide the insight required to back away from such a situation. It is a lot like the old lady who points out her son who is marching in the parade. She says "Look! My son is the only one in step!"
If problems on your project are repeating themselves, look around for the common denominators. When everything changes except a few faces, and the problems then are surfacing as problems again today, you need to be realistic. You can continue to blame the stream of resources who came, were bloodied, and left in defeat. Or you can find those things that aren't changing and ask why. If it didn't work before, and you've changed everything but X and it still isn't working. It would be reasonable to presume that X might be the problem.
Once you've identified the source of your Churn, you need to handle it cleanly. If you let any part of it remain, it will continue to reinfect your project unless completely removed. Like a virus or a cancer, you have to sterilize against it or the old behaviors and patterns that once responded to the source will recreate a new source.
It's worth noting that while these are generalizations, there are specific guidelines for identifying both of these issues. There are also very specific techniques that can learned for dealing with these issues and many others. Feel free to ping me if you'd like to know more.