Recently I noticed that when selecting an item in a category, the wrong item is displayed

EDIT: I disabled custom SEF settings and all works now. I will need to do some research on the custom SEF settings section before I use it by the look of it.
Does anyone have any advice/observations about that?

for example go to
ducks.org.nz/flight-magazine/content/81-flight-magazine-plus
and select any category - e.g.
ducks.org.nz/flight-magazine/content/158-issue-179
then select any article - e.g.
ducks.org.nz/flight-magazine/9-flight-magazine/81-flight-magazine-plus/issue-179/387/ramsar-status-for-wairio

But the item for a different article is rendered
Even though the URL still shows the selected target it actually renders:

ducks.org.nz/flight-magazine/9-flight-magazine/81-flight-magazine-plus/issue-169/81/plovers-go-to-russia-for-love

screenshot:
prntscr.com/vo97nk

I don't know where to look to figure out why it's happening

It also happens on other devices.
I have tried:
clearing the browser cache
opening on a different device
opening and re-saving some items
Deleting .htaccess
disabling SEO plugin
Disabling joomla rewriting

Un-publishing the russia article generates a 404 error

In the inspector, the base href is shown correctly, but the rendered page is always from ducks.org.nz/flight-magazine/9-flight-magazine/81-flight-magazine-plus/issue-169/81/plovers-go-to-russia-for-love

How does K2 call the content? Is it likely to be a data indexing problem?