If this topic was covered before I'm sorry ... but I found nothing.
I had a category page of my site ranking at about #10 in Google for a competitive generic search term for a long time. Now this page shows up at about #13 alternating with another 2 pages of my site. These pages are product pages and subpages of the category page. They are more specific i.e. focusing less on the generic search term but on the products. -
Curious: If I change settings to 100 results I find always 2 of these pages at about #20 and #21, alternating, too.
Ranking good with the category page is important for me even though #10 is no top ranking.
Other category pages with similar or better rankings don't move like this.
What does that mean? And what can I do?