Tried in Calc and Writer.
How to reproduce:
1. Open Writer
2. Write something if you want to (it doesn't matter)
3. Click File -> Save as
4. Move the mouse randomly
5. LibreOffice force closes.
The same happens with 'Open' dialog.
Launching LibreOffice from terminal and observing the messages gives, immediately before the force close:
QWidget::repaint: Recursive repaint detected
*** This bug has been marked as a duplicate of bug 69002 ***