Chosen Solution
About a month ago, my iPhone SE started doing something weird with Snapchat. Every time I take a flash photo with my rear camera, it double flashes then shows a poor quality picture (as if flash never happened). What can I do to fix it?
If that happens only when using snapchat but camera works as expected when taking a normal picture with flash, it’s probably just a bug. You may try uninstalling and reinstalling the App and see if that fixes the issue, otherwise you can try to contact Snapchat support and ask for their help.