I have the same app installed on 2 iphones, the Ipone 6 and Iphone X (IOS 12). Scrolling in the app works fine on the 6 both in the hybrid app and the browser. On the X it only works fine in the browser but within the hybrid app scrolling in pages is very laggy and slow. Not only scrolling: the overall performance seems to be much slower on the X. Note i'm talking about client side browser rendering performance: there is no interaction with a server. Any ideas? I already downgraded to UIWebview instead of WKWebview because of this issue (https://forum.mendix.com/link/questions/91916), but the downgrade didn't change the performance.
Is you want to see for your self go with an Iphone X to this URL
Scroll up and down and notice everything is pretty snappy.
Now do the same thing with the developer app, and notice it's very laggy / slow.
The problem is not related to the developer app, I also tried with own builds / latest phonegap CLI.
You can improve the performance a lot by removing the screenshot plugin from your hybrid app. This can be done by downloading the Phonegap package from Sprintr and customising config.xml to remove the following line: <plugin name="com.darktalker.cordova.screenshot" source="npm" spec="0.1.6" />
The downside is that the swipe to go back feature stops working.