nats-server: Route Error 'Unknown Protocol Operation'

Observed behavior

root@nats-02:~# journalctl -u nats -f
Oct 22 11:35:56 nats-02 nats-server[1227]: [1227] 2023/10/22 11:35:56.384916 [INF] 134.122.59.155:34810 - rid:17499 - Route connection created
Oct 22 11:36:12 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:12.624161 [ERR] 167.99.221.244:46548 - rid:17495 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:12 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:12.624190 [INF] 167.99.221.244:46548 - rid:17495 - Router connection closed: Parse Error
Oct 22 11:36:13 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:13.712144 [INF] 167.99.221.244:45838 - rid:17505 - Route connection created
Oct 22 11:36:14 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:14.909786 [ERR] 134.122.59.155:34810 - rid:17499 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:14 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:14.909832 [INF] 134.122.59.155:34810 - rid:17499 - Router connection closed: Parse Error
Oct 22 11:36:15 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:15.948951 [INF] 134.122.59.155:54398 - rid:17506 - Route connection created
Oct 22 11:36:28 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:28.716055 [ERR] 134.122.59.155:54398 - rid:17506 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:28 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:28.716083 [INF] 134.122.59.155:54398 - rid:17506 - Router connection closed: Parse Error
Oct 22 11:36:29 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:29.756519 [INF] 134.122.59.155:52766 - rid:17511 - Route connection created
Oct 22 11:36:42 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:42.494104 [ERR] 134.122.59.155:52766 - rid:17511 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:42 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:42.494645 [INF] 134.122.59.155:52766 - rid:17511 - Router connection closed: Parse Error
Oct 22 11:36:42 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:42.495021 [ERR] 167.99.221.244:45838 - rid:17505 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:42 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:42.495145 [INF] 167.99.221.244:45838 - rid:17505 - Router connection closed: Parse Error
Oct 22 11:36:43 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:43.582177 [INF] 167.99.221.244:50994 - rid:17516 - Route connection created
Oct 22 11:36:43 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:43.589974 [INF] 134.122.59.155:46270 - rid:17517 - Route connection created
Oct 22 11:36:47 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:47.103226 [ERR] 134.122.59.155:46270 - rid:17517 - Route Error 'Unknown Protocol Operation'
Oct 22 11:36:47 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:47.103251 [INF] 134.122.59.155:46270 - rid:17517 - Router connection closed: Parse Error
Oct 22 11:36:48 nats-02 nats-server[1227]: [1227] 2023/10/22 11:36:48.153274 [INF] 134.122.59.155:33910 - rid:17520 - Route connection created

Expected behavior

No errors

Server and client version

nats-server: v2.10.3 nats.ws: 1.18.0

Host environment

Digital Ocean Droplet

{
  "cluster": {
    "name": "nats",
    "port": 6222,
    "routes": [
      "nats://nats-node-01.fra1.prod.do.spreadfighter.cloud:6222",
      "nats://nats-node-02.fra1.prod.do.spreadfighter.cloud:6222",
      "nats://nats-node-03.fra1.prod.do.spreadfighter.cloud:6222"
    ]
  },
  "http_port": 8222,
  "jetstream": {
    "max_file_store": 10Gi,
    "max_memory_store": 0,
    "store_dir": "/data"
  },
  "lame_duck_duration": "30s",
  "lame_duck_grace_period": "10s",
  "pid_file": "/var/run/nats/nats.pid",
  "port": 4222,
  "server_name": nats-02,
  "websocket": {
    "compression": true,
    "no_tls": true,
    "port": 8080
  }
}

Steps to reproduce

No response