>>>>>Did you try to capture a coverage log. SET COVERAGE TO log.txt ? Then you can identify whether some unexpected code is run which is responsible for the delay?
>>>>
>>>>I had already searched for problematic code inside the various destroy events. I now did a SET COVERAGE and it revealed no special time consuming place. But more interesting is that it does not show the details of the native closing process at all!
>>>
>>>SET COVERAGE will only log VFP code and no internal processes.
>>
>>SET EVENTTRACKING is what should be used.
>
>Ah, this one indeed gives the time info of the destruction. But still not found the all explaining piece of code.

There's the related Set EventList, which is probably shortened by default, or else you'd get all the mouse motion etc. Check your list.