Opencv feature matching breaks on iPhone but not on simulator

I have Opencv C++ code running in a .mm file with a bridger to work on iPhone. In the simulator it works fine and has no problems. When running on an iPhone it breaks. Here is the code

 int minHessian = 400;
Ptr<cv::xfeatures2d::SURF> detector = cv::xfeatures2d::SURF::create( minHessian );
std::vector<KeyPoint> keypoints1, keypoints2;
Mat descriptors1, descriptors2;
detector->detectAndCompute( img1, noArray(), keypoints1, descriptors1 );
detector->detectAndCompute( img2, noArray(), keypoints2, descriptors2 );
//-- Step 2: Matching descriptor vectors with a FLANN based matcher
// Since SURF is a floating-point descriptor NORM_L2 is used
Ptr<DescriptorMatcher> matcher = DescriptorMatcher::create(DescriptorMatcher::FLANNBASED);
std::vector< std::vector<DMatch> > knn_matches;
matcher->knnMatch( descriptors1, descriptors2, knn_matches, 2 );
//-- Filter matches using the Lowe's ratio test
const float ratio_thresh = 0.8f;
std::vector<DMatch> good_matches;
for (size_t i = 0; i < knn_matches.size(); i++)
{
    if (knn_matches[i][0].distance < ratio_thresh * knn_matches[i][1].distance)
    {
        good_matches.push_back(knn_matches[i][0]);
    }
}

it specifically breaks on this line

matcher->knnMatch( descriptors1, descriptors2, knn_matches, 2 );

The error log specifies this as the error

libc++abi.dylib: terminating with uncaught exception of type cvflann::anyimpl::bad_any_cast

You have to remove #import opencv2/opencv.hpp and add the specific modules you need. In my case I needed these files

#import <opencv2/imgcodecs.hpp>
#import <opencv2/calib3d.hpp>
#import <opencv2/features2d.hpp>
#import <opencv2/xfeatures2d.hpp>
#import <opencv2/imgproc/imgproc.hpp>