"Only trigger when unique lines appear" doesn't seem to work for me

[schklom]

I am not sure this is a proper bug, or my misunderstanding of how this software works.

I want to monitor https://apps.nextcloud.com/ for changes.
The website sometimes moves items around, so I want to avoid these.

This is what I have done

and the other boxes on that page are empty.

but the box "Only trigger when unique lines appear" seems to be ignored as can be seen below

This happens often, even for other websites. Did I do something wrong, or is this an actual bug?