This is happening with SDK 37, on iOS, both with a built app or over expo-cli but only when in production mode.
As far as I can tell it happens after the network handshakes, while trying to upload an image directly to S3. The most useful log I could extract is this:
2020-08-18 23:37:32.854 [fatal][tid:com.facebook.ABI37_0_0React.NetworkingQueue] NSInvalidArgumentException: *** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]
Any ideas??