IL2CPP / Universal crash my game after splash

I just upgraded to Unity 5.1.
I have a game on app store, and when I tried to submit a bugfix update i ran into apples new reqirements, and I had to recompile the project with IL2CPP (Scripting Backend) and Universal (Architecture).
Now the app is crashing when the splash screen is displaying. (I had no problem on the Mono2x Scripting Backend).
See the attached image for xcode output.
I'm quite stuck at this point, so any suggestions will be very helpful!

 

Thank you for your suggestions.
I tried the 5.1 patch, but it's still crashing at the same point.

Another strange discovery after patching:
If I build the xcode project in unity and overwrites the existing it builds ok (in unity - still crash on device).
If I i then build the xcode project in unity using append to the existing i get errors in unity:
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KeyNotFoundException: The given key was not present in the dictionary.
System.Collections.Generic.Dictionary`2[System.String,UnityEditor.iOS.Xcode.PBX.PBXGroup].get_Item (System.String key) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:150)
UnityEditor.iOS.Xcode.PBXProject.GroupsGetByChild (System.String childGuid)
UnityEditor.iOS.Xcode.PBXProject.RemoveGroupIfEmpty (UnityEditor.iOS.Xcode.PBX.PBXGroup gr)
UnityEditor.iOS.Xcode.PBXProject.RemoveFilesByProjectPathRecursive (System.String projectPath)
UnityEditor.iOS.PostProcessiPhonePlayer.BuildXCodeProject (UnityEditor.iOS.ProjectPaths paths, UnityEditor.iOS.IncludedFileList includedFiles, System.Collections.Generic.List`1 frameworks, System.String sdkVersion, System.String targetOS, System.String productName, Boolean useIl2Cpp, Boolean installInBuildFolder, Boolean useSymlinks, Boolean isGameCenterUsed)
UnityEditor.iOS.PostProcessiPhonePlayer.PostProcess (UnityEditor.iOS.iOSBuildPostprocessor pp, BuildTarget target, System.String stagingAreaData, System.String stagingArea, System.String stagingAreaDataManaged, System.String playerPackage, System.String installPath, System.String companyName, System.String productName, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry)
UnityEditor.iOS.iOSBuildPostprocessor.PostProcess (BuildPostProcessArgs args)
UnityEditor.PostprocessBuildPlayer.Postprocess (BuildTarget target, System.String installPath, System.String companyName, System.String productName, Int32 width, Int32 height, System.String downloadWebplayerUrl, System.String manualDownloadWebplayerUrl, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:316)
UnityEditor.HostView:OnGUI()

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Error building Player: KeyNotFoundException: The given key was not present in the dictionary.

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I don't know if this has anything to do with the crash, but it's still strange behaviour.
I am trying to submit a report. My project is quite big, >4GB, packing report... (have no idea how long it will take).
EDIT: It is submitted now.

 

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