PiHole Drops Internet Bound Packets Randomly

[Gerowen]

So I've got a weird issue at my brother's house.  I help him self-host a couple of things at his house.  His setup is similar to mine.  He recently bought a "WoWe" mini PC (network card is Intel I225-V) to replace his raspberry Pi as a DNS ad blocker and VPN server.  I installed Debian on it and used PiHole and PiVPN to set up the ad blocker and VPN server; exactly the same as is running on my, also WoWe (Mine is newer with Realtek Ethernet), mini PC here at my house.  Mine and his both run Debian stable.  The biggest difference is that he insisted on having a GUI installed, so I set up a "dummy" xorg server that, instead of displaying to a monitor, displays to a virtual/dummy device.  This allows him to use RustDesk to graphically log in and do stuff on it without having an actual, physical display attached to it.  This is achieved with the package xserver-xorg-video-dummy .  Mine on the other-hand has no graphical utilities installed at all.  I installed Debian in headless/terminal mode, set up SSH, installed the services I wanted and left it alone.  Mine works great.  His on the other hand works "ok", but it randomly drops packets when communicating with the outside internet.

I first noticed it because we do most of our phone calls with Signal, which of course uses data.  He, most of the time, keeps a VPN connection back thru his house enabled on his phone, which forces his phone behind the PiHole, which has the effect of blocking ads for him on his phone even when he isn't home.  However, if his VPN is enabled, about once a minute I noticed all audio would drop for 5-10 seconds.  I also noticed that, when logging in via SSH to do any kind of maintenance (via the the VPN connection), that sometimes it'll just stop responding for 5-10 seconds and then everything I typed during that period will appear all at once.  To rule out the possibility of the issue being the VPN service I did some ping tests to the Cloudflare DNS servers (1.1.1.1), the Quad9 DNS server (9.9.9.9) and his own router from the mini PC itself instead of from my own machine via the VPN connection.  Pings to his own router always work fine.  Pings to anything outside his home though will, inevitably, have some amount of dropped packets.  The issue does not affect his router or any other wired device in the house.  Only this new mini PC seems affected.

He just purchased a brand new shielded network cable to go from his router inside to the ISP's hardware on the pole outside.  He also replaced the network cable going between the mini PC in question and the router.  I've used rfkill to soft disable the WiFi and Bluetooth cards, though I'm still seeing messages in journalctl referencing bluez starts and stops (probably because of the installed desktop environment).  I even tried killing the rustdesk service to see if that was it, but that didn't seem to help.

I'm debating on uninstalling the "nonfree" firmware for the network card and reverting to the FOSS driver, if there's any available, but I don't want to do that remotely so I'll have to go down there in person in the event doing so causes issues and I need the option of hooking up a monitor and interacting with it directly to reinstall a working driver.

At the same time though, I'm not completely convinced it isn't an issue with the router, except we've tried using different cables, different ports on the router, etc., and no other wired device is affected.  Only his PiHole/PiVPN server.

I'm just really at a loss for why, once a minute or so, it just starts dropping packets for a few seconds, then picks right back up like nothing was wrong.