After seeing that my wireless speeds were much faster than the speeds I was getting over Ethernet, I decided to invest in some new cables. I didn’t know it before, but I saw while I was changing them out that my current cables were Cat 5e. While putting my network together, I had just been grabbing whatever cables I could find in my scrap drawers. Now I have Cat 8 cables and my speeds jumped from 7MB/s to an average of over 40MB/s. It’s a much bigger improvement than I expected, especially for such a small investment.
Wonder if the cables replaced by OP were user-made, not commercial cables, that were our together incorrectly.
They had been collected from various ISP provided modems and routers I’ve purchased over the years.
At least in here some of the older modems, specially from ADSL-era, only had two pairs in them, so they were only good up to 100Base-T, which is roughly 7MB/s. So maybe check if that’s the case and throw those into recycling bin.