Why does the iPhone 6 Plus crash only?

I created an app with Swift and submitted it to iTunesConnect.

In less than an hour, I got a reply of reject (it was my first reject),
iPhone 6 Plus running iOS 8.1
The message was to reject to crash on the .

If you analyze the attached crash log,
The viewWillAppear method crashed in the first ViewController. All right.

So, here's the problem.
I don't have the actual iPhone 6 Plus, and I have
On the iPhone 6, iPhone 5, and iPad mini 2, these three devices have
The crash cannot be reproduced at all.

Also, I am using metal, so I cannot do the simulator test as it is, but
In the iPhone 6 Plus simulator, the metal implementation was removed, and the metal implementation is removed. It was not reproduced.

Some messages from iTunesConnect include
test method with release build,
How do I check if the building I'm testing is the same as the one I'm submitting?
is listed, and I have checked them, but
It cannot be reproduced in the release build, and the release build is a submit build and a
I was able to confirm that it is the same.

Under these circumstances, how should we deal with non-reproducible crashes?
I'm worried.The situation is quite limited and quite the same.
I don't think there are any, but if there are similar experiences and solutions,
I would like to ask you a question if you can give me a clue.

For example, in this app,
AVFoundation.framework (camera)
CoreMotion.framework
Metal.framework (Metal)
and other frameworks.
If you need additional information, we will respond accordingly.

Thank you for your cooperation.