What happened to us was Crashlytics decided to group only loosely related crashes, same uncaught Objective-C exception in the title field but totally different error message and root cause (displayed as subtitle).

But now we have fixed the original first issue, and the remaining crashes have a different message than the one that still appears in the subtitle field on Crashlytics dashboard, which causes confusion each time a new developer takes a look at the open crashes ("didn't we fix this one already?") before realising it's now a different issue.

It would be great if we could at least choose which crash instance is used in the title/subtitle, if not fully edit the title/subtitle values of crash groups.