Ios keyboard problem

I am trying to open my website with wkwebview. I have a comment bar and when I click the bar, keyboard opens. After that, when I close keyboard, there is white space on the page.

I tried to use IQKeyboardManager to fix it but interesting thing is it works fine in iOS 13.2 and above versions. But for example on iphone6 the problem continue.

How can I fix that? Any suggestion? Thanks