iOS Add to home screen is using private browsing

We are having an issue where add to home screen on iOS is using private browsing mode. This is an issue as we are using local storage for caching data.

Does anyone know if there is any meta data / config etc that is causing iOS to default to using private browsing? Private browsing is turned off when we try this.

This is our Ionic Info:

cli packages: (/usr/local/lib/node_modules)

@ionic/cli-utils  : 1.8.1
ionic (Ionic CLI) : 3.8.1

global packages:

Gulp CLI : CLI version 3.9.0 Local version 3.9.1

local packages:

@ionic/app-scripts : 2.1.3
Ionic Framework    : ionic-angular 3.6.0


Node : v8.4.0
npm  : 5.3.0 
OS   : macOS Sierra