Bad camera image quality on ios devices. Augmented Reality

Hi folks,
i am working on a BluePrint only AR app for a few months. Now it is near completion and works as expected on android devices.
On iOS devices however i ran into quite some problems. The main one is the strange camera image quality. It appears as if the camera has zoomed in quite a bit or cropped a big chunk out. It also has really bad image quality compared to the iOS camera app.
The first picture is taken with a blank AR project but this is basically how it looks in my app.
Any hint on how to solve this issue would be appreciated.

Some further information:

I started the project with an ARcore template on engine version 4.20 on Windows PC. For iOS deployment i had to switch to Mac and 4.23 because 4.20 had a shader compiling issue.
Xcode 11 / MacOS Catalina 10.15 / iphone 6s, iPad Pro 12.9 inch / iOS 13.1.3 / UE4.23