R620 Constant Ethernet Dropouts

G'day all,

I've had a used R620 for a few years now, and it's been fantastic... apart from one issue that's plagued it as long as I can remember. I've done everything imaginable to try to diagnose this, but no avail. I've spent hours looking through dmesg, syslog, Reddit, forums; you name it, I've probably tried it. I've made posts to multiple forums and subreddits, even spoken to some devs of AlmaLinux.

Now, the actual issue: Ethernet constantly drops out, and is getting more frequent. It started as something I barely noticed, then moved to a 10-20 second dropout every ~15 minutes, and now it's more like a 30-60 second dropout every 15 seconds. I can't even run updates without putting aside a full day just to do so.

I've tried changing BIOS power/performance profiles, 2 different NICs besides the standard included 4x1gb NIC, disabled EEE, tried LAGGs, reinstalled the OS, and a few other things that I can't recall atm.

Has anyone else come across an issue like this? Any other suggestions? I'd really like to fix this issue, rather than spool up a different device. I have an R720 as well but I don't have the time to set that up for the foreseeable future.

EDIT: I've also tried swapping the dual CPUs, and running with a single CPU (and tried both of them to rule out a dying CPU).