roachtest: ssh_problem failed

roachtest.ssh_problem [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyAwsBazel/21473010?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachtestNightlyAwsBazel/21473010?buildTab=artifacts#/ycsb/E/nodes=3/cpu=32) on release-25.4.15-rc @ [4913a926920d3003e1223156615a6a6a7d524b59](https://github.com/cockroachdb/cockroach/commits/4913a926920d3003e1223156615a6a6a7d524b59):

```
test ycsb/E/nodes=3/cpu=32 failed: (test_runner.go:901).func4: cluster.PutE: put "/go/src/github.com/cockroachdb/cockroach/bin/cockroach.linux-arm64" failed: error persisted after 3 attempts: TRANSIENT_ERROR(ssh_problem): ~ scp -r -C -o StrictHostKeyChecking=no -o ConnectTimeout=10 -i /home/roach/.ssh/id_rsa /go/src/github.com/cockroachdb/cockroach/bin/cockroach.linux-arm64 ubuntu@3.133.85.182:./cockroach
client_loop: send disconnect: Broken pipe
lost connection: exit status 1 [owner=test-eng]
```

Parameters:
- arch=arm64
- cloud=aws
- coverageBuild=false
- cpu=32
- encrypted=false
- runtimeAssertionsBuild=false
- ssd=0
Help

See: [roachtest README](https://github.com/cockroachdb/cockroach/blob/master/pkg/cmd/roachtest/README.md)

See: [How To Investigate \(internal\)](https://cockroachlabs.atlassian.net/l/c/SSSBr8c7)

_Grafana is not yet available for aws clusters_

Same failure on other branches

- #173555 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.2.23-rc]
- #172557 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.4.14-rc]
- #172517 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-25.2.22-rc]
- #172515 roachtest: ssh_problem failed [O-roachtest O-robot T-testeng X-infra-flake branch-release-26.1.8-rc]

/cc @cockroachlabs/test-eng

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*ssh_problem.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Start with the roachtest README and the failure at test_runner.go:901, then inspect the linked TeamCity log and artifacts for the AWS arm64 ycsb/E run. Investigate why the scp transfer ends with a broken pipe across the listed branches; done means the ssh_problem failure is understood and the affected roachtest behavior is fixed or reliably diagnosed.

Written by the indexing model from the issue text.