iOS purpose strings

Apple support is driving me nuts. It's probably not their fault, but it's still infuriating. This has been going on for 2 months now and I am rather frustrated.

When uploading my Archive to the appstore everything works fine, but apple then does some processing on the app. This process either crashes or just silently fails resulting in my build not being accepted. It runs fine on my phone.

The most information I got was this:
In case you don’t have the previous email, I am forwarding you again the information available for this. Please review them all and follow the instructions because there is all the information you need to fix the issue.

Starting with iOS 10, purpose strings are required for access to any protected class of data from within your app, including protected data classes by any third-party library your app uses. If you're receiving a message about a missing purpose string for a data class that you don't recognize, consult with your third-party library vendors about using that protected data class.
For more detailed information, consult the following resources:

• App Programming Guide for iOS: Supporting User Privacy
• Information Property List Key Reference: Cocoa Keys
• WWDC 2016: Engineering Privacy for Your Users (using description keys is discussed at 29:14)

If you have additional questions related to this request, please reference case number xxx.

As you may have noticed, there is no actual bug report included. I've asked uncountable times for an actual bug report, but maybe there really is none. So all I get is this very vague information, that something is wrong with a purpose string. There are about 50 purpose strings and I am not going to check them all, as it takes forever. I guess by now I would have tested them all, but this is just terrible reporting.

I'm wondering how to find out what purpose string could be required by my app. As far as I know I don't need any rights at all, but obviously apple disagrees.

Support also told me to ask Unity as they don't support 3rd Party Applications, bla bla bla. It's obviously an apple problem, but they are unwilling/incapable of helping.

edit: I've decided to jump in and start adding all purpose strings, let's see if this will resolve it.

 

Are you using ads or analytics or anything?

 

I'm using IAP, but I've found the culprit... well to some extent. Apple thinks I am accessing the Camera and wants me to add a purpose string description for that. Now I only need to find out what makes Apple think so.

 

Found it. I added a QR generator, but it was also a reader. This used the WebcamTexture -> Camera access....