Google has been doing some strange things to my rankings for some categories lately. Essentially something I normally rank on the first page for I will get moved to the second or third page (or lower) because Google changes a relevant category page to what they say is a better page that is my home page. But my home page doesn't really have anything to do with these search terms so it is moved down the rankings. When I re-submit the proper url Google says it chose my homepage as canonical over what my site says is canonical. Rankings go back to normal when I do this but with about 1000 categories it is impossible to keep track of what ones are changing and when I need to do a resubmit. Anyway, I reached out for some SEO help and was told the following:
Well I just took a look at your site. It has an issue and strange at that. Here let me show you what I mean. See the image below. It has a double canonical. The fact that you have a dbl canonical is the issue. You need to fix this. This is a coding error. This double canonical is also present on all pages I check. Also all of your paginated content for comic decals, they all point to the 1st page of product as the canonical. This isn't the most optimal setup btw.
So I checked into what they said and it is true for a LOT of my category pages and even product pages. Many have duplicate "HTML Rel-Canonical" tags from what this plug in (LinkResearchTools/Link Redirect Trace) is showing me. Odd that about 1/4 of my page/categories/products are showing the duplicate canonical.
Not sure I totally understand about the comment "they all point to the 1st page of the product as canonical" either.
I do have the SEO ultimage add-on but disabling that doesn't seem to fix anything so that doesn't appear to be causing the issue.
The page I'm referring to is https://fastdecals.com/shop/comic-cartoon-decals/but this is happening all over the site. Any help or input would be appreciated.