WKWebview behaviour change after iOS 13.4

I recently updated my app from UIWebView to WKWebView. I am now having some issues with WKWebView for versions above iOS 13.4.

The user actions is WKWebView is managed using JavaScript.
I added event.preventDefault() in action for touchStart event. It is preventing events from propagating further in iOS > 13.4(ex: Pan gesture won't be detected as touch event is prevented from further actions). But it is working fine below iOS 13.4(Pan gesture is detected).

Any idea about this behaviour?

Was there any major API changes for WKWebView or WebKit in iOS 13.4?