QPropertyAnimation strange behavior only on Ubuntu

[atomic]

Hi, I use following code to create "drop-down" dialog when user click 'more' button

QPropertyAnimation *animation = new QPropertyAnimation(this, "size");
animation->setDuration(150);
animation->setStartValue(QSize(this->width(), this->height()));
animation->setEndValue(QSize(this->width(), 360)); // on start has 250
animation->start(QPropertyAnimation::DeleteWhenStopped);

QPropertyAnimation *animation = new QPropertyAnimation(this, "size");
animation->setDuration(150);
animation->setStartValue(QSize(this->width(), this->height()));
animation->setEndValue(QSize(this->width(), 360)); // on start has 250
animation->start(QPropertyAnimation::DeleteWhenStopped);

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and it works fine on windows but on ubuntu this code on every time when is called ( when user click 'more' button ) also moves dialog for top-left corner. Can you check this code on some linux distribution on simple dialog form?
What I am doing wrong? Maybe it is a bug Qt?

Thanks,

Edit.
Now i see that simple resize without animations

this->resize(this->width(), this->height()+360);

this->resize(this->width(), this->height()+360);

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also moves my dialog window... why? How I can resize window on ubuntu / linux? It is problem of my code? System? Qt?
On Windows the same code works properly.