I have dealt with this issue in the past and confirmed it's not caused by a damaged cable nor any hardware issue. I replaced them just in case with brand new cables and the same issue was happening.
Previously it was only resolved by upgrading to a different OpenWRT version, now it seems like the very same issue is back. I'm not sure if it reappered in 23.05, could've reappeared in any version between 22.03rc and 23.05.0-rc3 as I hadn't updated it until now.
I documented the whole issue in the past in this thread Internet speed capped at 100mbps by the router
I also see there's a related bug report on github, other people are reporting it too https://github.com/openwrt/openwrt/issues/9069
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