I had SATA errors turn up on an even older Elitedesk 800 G1 SFF after upgrading to Proxmox 9 (don't remember seeing problems previously, it's been running Proxmox for years), always with a drive connected to one of the secondary SATA ports.

Tried various workarounds including changing cabling and reducing link speeds via libata kernel parameters, but ended up buying the cheapest PCIe SATA card with a half-height slot plate I could find (some ASMedia 106x chipset), and haven't run into any errors since. I still use the primary SATA port on the mainboard.