A SIGSEGV is a segmentation fault. If you can't get enough information about where the issue might be happening from the crash report from the device, then you will have to do use a divide and conquer method of figuring out what the problem is.
Hopefully you are using source control like GIT to keep track of your source code, so use that and go back to an older version of code that will generate an application that will work on iOS 6.1.3. When you find the working code base, that's your starting point and the latest code base is the failing version. Now find a commit half way between the working and failing and test again. If the half way point works, that's the new good starting point and continue this.
If you ARE using GIT, look into "git bisect" to help you do this a lot faster..
Short of that, if you are the developer, you have access to the sources and are the best equipped to fix this issue, we cannot really help you.