iPhone camera app switches off when/after taking photo

Some odd behaviour crept up after the 17. October (last time it didn't show that problem). When I try to take a photo with the back camera the camera app closes when I "push the trigger", either before taking a photo or shortly after. In some cases it switches off the app, sometimes the screen also goes black (but on pressing home button coming back).

Weird thing is, video, slo-mo, time lapse all work without shutting down the camera app.

iOS 13.1.3, iPhone 7