Gamelift ProcessEnding and Destroy via suggested sample, but reported SERVER_PROCESS_PROCESS_EXIT_TIMEOUT

https://docs.aws.amazon.com/gamelift/latest/developerguide/integration-server-sdk5-csharp-actions.html#integration-server-sdk5-csharp-processending

We use unity dedicated server(2021.3.10f1) and sdk C#(5.1.1), managed fleet with linux.

We got dedicated server issue, started remote monitoring with ssm. And tail whitewater/Logs/processmanager.log

Case 1, use sample. reported SERVER_PROCESS_PROCESS_EXIT_TIMEOUT.

GenericOutcome processEndingOutcome = GameLiftServerAPI.ProcessEnding();
GameLiftServerAPI.Destroy();

if (processEndingOutcome.Success)
  {
    Environment.Exit(0);
  }
else
  {
    Console.WriteLine("ProcessEnding() failed. Error: " + processEndingOutcome.Error.ToString());
    Environment.Exit(-1);  
  }

ProcessExitHelper: Determining exit from processExitValue 137; terminationReason
ProcessExitHelper: Creating abnormal exit from exitCode FORCE_EXIT_EXIT_TIMEOUT
EventReporter: Reporting exit ProcessExit(exitType=ABNORMAL, exitCode=FORCE_EXIT_EXIT_TIMEOUT) with exit code 137 for process [`process_uuid`] 
EventReporter: Did not find an abnormal exit, but FORCE_EXIT_EXIT_TIMEOUT exit code. must report
....
HeartbeatHandler: Received Heartbeat response with Status: [Active]; Unhealthy processes: [[`process_uuid`]]; Unregistered processes: [[]]
GameProcessManager: Skipping process termination; no managed process found with process UUID `process_uuid`

Case 2, use sample line of only ProcessEnding. but not reported SERVER_PROCESS_PROCESS_EXIT_TIMEOUT.

GenericOutcome processEndingOutcome = GameLiftServerAPI.ProcessEnding();

ProcessExitHelper: Determining exit from processExitValue 0; terminationReason null
EventReporter: Reporting exit ProcessExit(exitType=NORMAL, exitCode=NONE) with exit code 0 for process [`process_uuid`]
EventReporter: Did not find an abnormal exit.  Not recording an event.
...
HeartbeatHandler: Received Heartbeat response with Status: [Active]; Unhealthy processes: [[`process_uuid`]] Unregistered processes: [[]]
GameProcessManager: Skipping process termination; no managed process found with process UUID `process_uuid`

Which one is normal? what does HeartbeatHandler Unhealthy processes list mean?

As an aside, the server would sometimes restart and show SERVER_PROCESS_EXIT_TIMEOUT when I wasn't playing.