The test failed on branch=release-21.1, cloud=gce:
test artifacts and logs in: /home/agent/work/.go/src/github.com/cockroachdb/cockroach/artifacts/backup/mixed-version/run_1
	test.go:288,assertions.go:262,assertions.go:1332,require.go:1035,backup.go:186,versionupgrade.go:200,backup.go:246,test_runner.go:733: 
			Error Trace:	backup.go:186
			            				versionupgrade.go:200
			            				backup.go:246
			            				test_runner.go:733
			            				asm_amd64.s:1581
			Error:      	Received unexpected error:
			            	dial tcp 35.238.192.232:26257: connect: connection refused
			Test:       	backup/mixed-version

	cluster.go:1667,context.go:89,cluster.go:1656,test_runner.go:820: dead node detection: /home/agent/work/.go/src/github.com/cockroachdb/cockroach/bin/roachprod monitor teamcity-3824371-1638342455-07-n4cpu4 --oneshot --ignore-empty-nodes: exit status 1 3: 10427
		4: 10350
		1: 12591
		2: dead (exit status 7)
		Error: UNCLASSIFIED_PROBLEM: 2: dead (exit status 7)
		(1) UNCLASSIFIED_PROBLEM
		Wraps: (2) attached stack trace
		  -- stack trace:
		  | main.glob..func14
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1147
		  | main.wrap.func1
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:271
		  | github.com/spf13/cobra.(*Command).execute
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:830
		  | github.com/spf13/cobra.(*Command).ExecuteC
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:914
		  | github.com/spf13/cobra.(*Command).Execute
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/vendor/github.com/spf13/cobra/command.go:864
		  | main.main
		  | 	/home/agent/work/.go/src/github.com/cockroachdb/cockroach/pkg/cmd/roachprod/main.go:1889
		  | runtime.main
		  | 	/usr/local/go/src/runtime/proc.go:255
		  | runtime.goexit
		  | 	/usr/local/go/src/runtime/asm_amd64.s:1581
		Wraps: (3) 2: dead (exit status 7)
		Error types: (1) errors.Unclassified (2) *withstack.withStack (3) *errutil.leafError