Rendering issue on new iPhones

Hi all,
hope this is a good place to post this thread.

I’m having a strange problem on some devices. It seems a random behaviour (see attached images).

The app was developed on Unity 2017.1.3 with Kudan Unity Plugin v1.4

Tested devices:
iPhone 6 iOS 12.1.2 OK
iPhone 8 iOS 12.1.2 PROBLEM
iPhone 8 iOS 12.1 PROBLEM
iPhone X iOS 12.1 PROBLEM
iPad Pro 12.1.1 OK
Android Samsung Galaxy s7 PROBLEM
LG Nexus 5 OK
Moto G 2 OK

I am writing here because I don't know if it is a Kudan realted issue. Actually I don't think so, since I tested with same Unity and Kudan versions, but with different project settings and I am not having this results in the affected models.

That's why I'm starting to think it could be related to rendering, lighting or project settings.
I'm excluding shaders because with the same prefab in other projects I am not having any problem.

Also, the most interesting thing that you can see from the attached images is this strange behaviour where if I'm very near to the model, that strange glaze gradually disappears. So it could be even not an AR problem at all.

Any ideas would be highly appreciated.
Thank you!