Also appears to affect www.jkowners.com forum (though there's a good chance it is the same platform if not site as jeepforum.com)

Jeepforums looks to be based off of ohoBB from what I can tell., same for jkowners.com. While Safari fails more gracefully, I can indeed see it crashing and reloading on Safari, but the problem is much more pronounced on Chrome in comparison. It seems related to which ads are being served on the topic thread from which ad service. 

Not only can it result in a partially loaded page on Chrome, it is super janky on scroll, and depending on which ads are loaded and how, can mess up the session history - if you press back it will just keep reloading the page if the last load was an ad reload or update on the same page.

Screenshot of safari: https://drive.google.com/file/d/0By4O1f2IQqQ_MkxGbTM4a3U4cUE/view
Screenshot of Chrome for iOS: https://drive.google.com/file/d/0By4O1f2IQqQ_MFdkZ2xTOG1hUzQ/view

The jank exists on iOS9, and I can also repro the page crashing in iOS9, so I don't think this is specific to iOS11.

This bug is reproducible with ios_web_shell and not reproducible with test WKWebView app and Chrome User Agent. 

But is not reproducible in ios_web_shell after removing all injected scripts.

Works fine after removing navigation.js scripts. Should be fixed by Danyao's refactoring.