WinDev 11 (WinDev 12??) ThreadExecute Problem

Hello!

I have a problem with ThreadExecute. ThreadExecute works, no doubt, but if I'm working in a thread, with hyper file commands like hreadfirst or hmodify then I have several times, on slow machines the index (.ndx) corrupt on classic hyperfile. Can someone help me? Is Multitask(-1) or MultitaskRedraw(Window) a problem?

This is my code (shortend):

in Main (initialization of window):

ThreadMode(threadCriticalSection)
ThreadExecute("MAINLOOP",threadUseHyperFile,TimerMain)
ThreadWaitSignal(Infinite)

In TimerMain:

ThreadListe is int

ThreadSendSignal(".")

LOOP
 
  ThreadWaitSignal(300)

  IF ThreadState("TMR")=threadRunning THEN
    ThreadListe=BinaryOR(ThreadListe,1)
  END

  IF ThreadListe=0 THEN
    ThreadExecute("SENDEN",threadUseHyperFile,SendenEmpfangen)
  END

END

SendenEmpfangen (Send/Receive):

HReadSeek("XXX_","KEY",1)
IF HFound("XXX_") THEN
  HCopyRecord("XXX_",XXX)
  HModify("XXX_")
  RESULT False
ELSE
  HCopyRecord("XXX_",XXX)
  HAdd("XXX_")
  RESULT True
END