The more you work with Revit the more likely you are to run into demons in the data. What do I mean by demons? Demons are unexplained behaviors. I'm not talking about software bugs that won't go away until you've installed a software update. I'm talking about errors in the data of the project file itself. Errors that can be repaired by replacing the corrupt data with an arbitrary value and then changing it back again.
Somehow, the process of changing the offending data to something arbitrary, then changing it back to the way it should be can remedy unexplained behaviors. I'm not talking about changing a value and then hitting the undo command. I'm talking about using Revit's tools to change the data to something arbitrary then changing it back... like the change is some new data for the model. It's just a matter of isolating the parameter values that are causing the unexplained behaviors... then finding the right combination of commands that will reset or refresh the offending data. These commands might include flexing parameters, cut & paste in same place, mirror, nudging, or possibly other commands. Let me give you some examples...
I upgraded a model once, from Revit 2009 to Revit 2011, and an odd thing happened. In hidden line mode, half the doors and windows had shaded glass (by design) while the other half had no shading. And it wasn't like there was any consistency... the shading was gone from random doors and windows. I realized at that point that I had a demon in my data, so I went into the offending material (glass) and set the surface pattern of the glass material to none (it was the surface pattern that was not cooperating), then changed the surface pattern back to solid fill to get this glass material to show properly everywhere.
Another thing that happens a lot... I like to nest families into a host family and link the parameters of the nested family and its host family, but once in a while after making a change to a nested family and loading it back into the host family, solids disappear or just don't flex when the family is loaded into a project. I have to flex some of the linked parameters, while still in the family editor, to reset or refresh the offending data.
Wall cleanups at intersections (not to beat a dead horse) can also cause demons. Sometimes nudging one of the walls can cleanup your intersection. Sometimes you have to cut a wall to your clipboard and paste it back into the same place to get intersections to heal properly. In fact, when any family (that was working fine before) isn't cooperating try a cut and paste in same place. This can reset data in the model.
If any of my readers are familiar with a particular demon please feel free to leave a comment describing the demon and how you "exorcised" it.