Prometheus helmrelease: unable to yaml.Unmarshal

$ kc -n oas get hr  monitoring
NAME         RELEASE      STATUS     MESSAGE                  AGE
monitoring                                 unable to yaml.Unmarshal [35 32 68 101 112 101 110 100 105 110 103 32 111 110 32 119 104 105 99 104 32 68 78 83 32 115 111 108 117 116 105 111 110 32 121 111 117 32 104 97 118 101 32 105 110 115 116 97 108 108 101 100 32 105 110 32 121 111 117 114 32 99 108 117 115 116 101 114 32 101 110 97 98 108 101 32 116 104 101 32 114 105 103 104 116 32 101 120 112 111 114 116 101 114 10 99 111 114 101 68 110 115 58 10 32 32 101 110 97 98 108 101
…
1 34 93 10] from values.yaml in Secret oas/monitoring-settings   9m14s

see https://open.greenhost.net/openappstack/openappstack/-/jobs/11837