runtime problem in modeless dialog with events OnMouseEntered OnMouseMovedOff

hello,
i have a runtime problem in modeless dialogs with events OnMouseEntered and OnMouseMovedOff (example for testing is attached).

if i click on run-button and let the mouse on this button or move the mouse to cancel-button or progress bar or outside the dialog, then the process needs 11 sec.
if i click on run-button and move the mouse in the form, then the process needs 15 sec.
if i click on run-button and move the mouse to the dark grayed field on top, then the process needs 18 sec.

edit:
if i disable the events, then is it ok in all cases.

what can the problem be?

best regards
marco