Is the iOS app open source?
I don’t code and couldn’t do anything myself, but maybe there would be some interest in looking at it and making the app usable again.
I’m now stuck with 18K images and an unusable app - caused by an old problem 
http://mapillary.trydiscourse.com/t/bugreport-latest-ios-app-crashing/2712
http://mapillary.trydiscourse.com/t/bugreport-app-periodically-hangs-when-there-are-a-lot-of-images/3903