Unraid presumably crashing AmpliFi HD router and household internet

I know the title is a little misleading, sorry about that.

For the past week, I've had my internet disconnect (all devices) and reconnect at 9,6/8.3 mbps (oddly specific). The only way to get it back up to 100/100mbps is to disconnect all ethernet connected devices and power cycle the router then plug everything back in when speed is back to normal.

• I've tried resetting the router, downgraded and upgraded firmware, disabled NAT according to AmpliFi's KB, but the only thing that works is to not power up my Unraid server which resides on an Intel NUC which boots 6.9.2 via UEFI.
• I've disabled everything related to secure boot, Thunderbolt, etc, which I don't require and I can't see any network settings in the BIOS setup menu. When I attempt to start the Unraid server, internet works fine for a couple of minutes and then immediately dumps, which I assume is when Unraid does some internal network stuff related to bridging, etc.
• I've also tried disabling both bonding and bridging. I tried enabling IPv6 in the router config and in Unraid, but that didn't do the trick.
• I've tried re-creating my flash drive and I'm on a completely fresh installation, no Docker service or VM:s enabled at all, not even a single plugin.
• I've ran a memory test (built in at Unraid boot menu) which showed no failures.
• I've swapped all ethernet cables to brand new cables.
• I've connected a laptop directly to the in-wall ethernet jack (ISP, no modem), which gives me a flawless 100/100mbps connection, no issues.

I'm in a conversation with the AmpliFi support which are asking me to do the same thing over and over again (reset, power cycle, send support info, disconnect hardware, call ISP and ask for outages), which I've completed numerous times the past week.

I've also bought an ASUS TUF router which I'll pick up and try out later tonight, but until then, maybe someone in the forums can give me any advice?