I get this error frequently from my testers on their iPhone 4 - no crash on iPhone 5s, iPad Air, iPad mini, not even on an iPhone 3GS.
I thought it's memory related, but according to instruments I only need up to 14MB during that operation, and Crashlytics shown available RAM of 120 MB - so I guess that's not the problem, right?
What else could be the cause for that crash? It happens during the downloading of files with FTPManager (https://github.com/nkreipke/FTPManager).
3 ... FTPManager.m line 370
-[FTPManager _downloadFile:toDirectory:fromServer:]
24 ... FTPManager.m line 475
-[FTPManager downloadFile:toDirectory:fromServer:]