IWServer as service become unresponsive

[dabuzu]

I am using IW 14.2.9 ultimate with Delphi 10 Seattle 
Installed components : TMS and CGDevTools
External connection is done thru an proxy server.

I encounter a strange situation, service is running ok several days, but are moments when become unresponsive.
Server processor goes above 25 % and everything respond in 10-20 sec or even get timeouts.

Restarting service do not solve the problem, because instantly server get back to 25-30 %. Memory consumption is not height and third server (database layer) is working ok for other clients as well.

I did also a new installation of  IW service on second server and from proxy I activate which server to run. But when are problems, Proc constantly > 25 % switching servers do not solve anything. Second server goes instant to the same proc usage and also become unresponsive.
That takes  from 5 min to 40 min, till everything goes back to normal and server respond in milliseconds.

What I didn't understand, is , when busy, why do not show at list page of login (that is simple and do not connect to any third party service) when start.
Why server does instantly at 25-30 % when restarting ?!
In logs are nothing strange, no exceptions reported.

Please, any suggestion is very welcome.

config:
  self.RestartExpiredSession := True;
  Self.BoundIP := FConfig.CFG.ReadString('Server','BoundIP',False);
  self.Port := FConfig.CFG.ReadInteger('Server','BoundPort',False);
  self.AllowMultipleSessionsPerUser := false;


 Self.SessionTimeout := 120; {2 hours}
 Self.FilesDir :=  Self.ContentPath + FConfig.CFG.ReadString('Server','SharedFilesDir',False);
 Self.InternalFilesDir := Self.ContentPath + FConfig.CFG.ReadString('Server','SharedFilesDir',False);


TIWSecurityOptionsAccess(Self.SecurityOptions).mCheckSameIP := False;
TIWSecurityOptionsAccess(Self.SecurityOptions).mCheckSameUA := true;
TIWSecurityOptionsAccess(Self.SecurityOptions).CheckFormId := true;
SecurityOptions.ShowSecurityErrorDetails := False;

CookieOptions.SessionCookies := false;
CookieOptions.HttpOnly := true;
CookieOptions.UseCookies := True;

  self.JavaScriptOptions.AjaxErrorMode := emNone;
  self.LogCommandEnabled := true;
  self.LogSessionEvents := true;

  self.ExceptionLogger.RegisterIgnoreException(EConvertError);
  self.ExceptionLogger.RegisterIgnoreException(EUnknownBrowserException); {Unknown browser type}
  self.ExceptionLogger.RegisterIgnoreException(EInvalidSession); {Invalid session}
  self.ExceptionLogger.RegisterIgnoreException(EExpiredSession); {Expired session}
  self.ExceptionLogger.RegisterIgnoreException(EIWNoSessionId); {No session ID}

  self.ExceptionLogger.LogType := ltFile; // ltEventLog;
  self.ExceptionLogger.FilePath := Self.ContentPath + 'Exceptions\';
  self.ExceptionLogger.FileName := 'Exceptions.log';
  self.ExceptionLogger.PurgeAfterDays := 1;
  self.ExceptionLogger.Enabled := True;