Flaky connection between iceland and west coast us (lags/dropouts)

### What is the issue?

I have a server in Iceland and my workstation in SF. The connection is very flaky and sometimes drops out entirely.

I first noticed this trying to set up kube, where a node would come up and then disconnect from the controller after a bit. I can replicate the flakyness by just pinging my workstation from the server -- sometimes the ping is 180 ms, sometimes 12000 ms, sometimes it times out. tailscale ping is always 180 ms.

I can things not over tailscale from the server, and my direct ssh connection is rock solid.

Is there a work around? I can handle higher but constant pings -- one colleague said I might be able to force DERP? I can't see how, but am curious if it's posible.

BUG-e6260b15e0b01c2ab9021951eea3cb066f0b1911c4cfedd1d85dee73e2558dcb-20250227020026Z-83c01e6383147fbb

### Steps to reproduce

ping -c 100 tom-workstation

### Are there any recent changes that introduced the issue?

_No response_

### OS

Ubuntu 22.04.5 LTS (both server and workstation)

### OS version

Ubuntu 22.04.5 LTS (both server and workstation)

### Tailscale version

1.80.2
tailscale commit: 62b8bf6a082c4bea1b9e6ee1962c81c6ee5263d3
other commit: 3c35ee9872cbeac18fbf544a96e594ab9e9f05a4
go version: go1.23.5

### Other software

None, fresh node.

### Bug report

_No response_