Position of QMessageBox

[Raadush]

I quite dont understand this issue. I have this part of code:

x=500;
y=500;
message->move(x,y);
message->exec();
r=p11manipulator->thread.functionReturned;
 
if(!r)
{
     message->move(x,y);
     message->exec();

x=500;
y=500;
message->move(x,y);
message->exec();
r=p11manipulator->thread.functionReturned;

if(!r)
{
     message->move(x,y);
     message->exec();

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message is created in constructor of my class with message = new QMessageBox(this); and "this" is QMainWindow. When I call message->exec() for the first time, it is placed somewhere (500,500 i hope), but for the second time, it jumps slightly higher. Why is that?