Probably just being thick, but when I tap on any thread in unread content since the upgrade it takes me back to the very first post not the latest one.

What am I doing wrong?

You need to click on the tiny red dot to the left of the thread title to take you to the first unread post. The tiny red dot is almost impossible to press on a phone with sausage fingers though.

In the latest version of the forum software if you click on the main text it will take you to the first post (this is by design).

To go to the first unread post, you need to click the small dot/star to the left of the topic or click on the timestamp.

On mobiles, we've tried to make the dot/star slightly bigger - but I still think it is an issue.

I've raised the issue directly with the developers.