iPhone6, iOS 12.5.5.
Several latest Mapillary app versions.
Two types of hangs observed:
a) When taking pictures and several thousands of images are there, it somewhat frequently stalls. In most cases it “unfreezes” on its own.
b) When uploading, it freezes permanently. App does not update or respond to controls.
Switching away from the app and back to it results in it crashing.
Observed with 15-35GB of images (image count not shown by the app anymore).