Watchkit`s WKInterfaceImage setImage causes "Terminated due to Memory error" - ios

Question

I want to animate images on a watch (like the activity app, if you´re interested, but it´s not important for this problem)
I draw images in a loop first: GlanceController.m
NSMutableArray *images = [[NSMutableArray alloc] init];
for(int i = 0, j = 0; i < 10; i++, j++){
#autoreleasepool {
// ...
UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
// ...
// create UIImage and save it to an array for later
UIImage *ejCircle = UIGraphicsGetImageFromCurrentImageContext();
[images addObject: ejCircle];
ejCircle = nil;
UIGraphicsEndImageContext();
}
}
So far everything works fine, thanks to autoreleasepool, the memory consumption is not too high here, (about 5 mB before autoreleasepool gets drained back to 2 mB)
However now I try to animate this in a WKInterfaceImage, I get a Memory Error:
// take the array and create an animated image out of it
UIImage * img = [UIImage animatedImageWithImages:images duration:1.0];
// memory about normal 2 mB after this line
[wkInterfaceImage setImage:img]; // APP CRASHES HERE
// memory consumption jumps to 30 mB after this line: too much
// for the watch app, the app gets terminated.
[wkInterfaceImage startAnimatingWithImagesInRange:NSMakeRange(0,50) duration: 1.0 repeatCount: 1];
My question is, why the app crashes in this line. The memory consumption explodes, but I don´t alloc/malloc/new something here.
Edit
I just found this crash log in XCode Devices:
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Identifier: MyApp WatchKit Extension
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Version: ???
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Code Type: ARM-64 (Native)
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Parent Process: debugserver [620]
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Date/Time: 2015-07-14 16:04:04.134 +0200
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Launch Time: 2015-07-14 16:03:42.401 +0200
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: OS Version: iOS 8.4 (12H143)
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Report Version: 105
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Exception Type: EXC_RESOURCE
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Exception Subtype: MEMORY
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Exception Message: (Limit 30 MB) Crossed High Water Mark
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Triggered by Thread: 0
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Thread 0 name: Dispatch queue: com.apple.main-thread
Jul 14 16:04:04 iPhone-6-Plus ReportCrash[622] <Error>: Thread 0 Attributed: