I downloaded a third party camera app and it works fine. The one I downloaded is called MuseCam. That makes me believe the issue is somehow software related rather hardware. My lens is shaking so hard when using the original Apple camera app that I can here the shaking noise. Like if there is a fly caught inside the phone! Looking at the lense closer also reveals how violently it is shaking.
Anyways, from now on I will use that third party camera app.
Material:iPhone 6S+. 128Gb. iOS 11.3.1.