We are using PySide so this could be a PySide bug. Migrated from Qt5  to Qt6. This issue was not present in Qt5. There's a main window from which several non-modal dialogs can be opened. When one such dialog is opened and the main window is moved or resized, the dialog automatically starts shrinking until only the title bar is visible. It can be manually resized again but as soon as the main window is resized or moved, the size of the dialog(s) starts shrinking. I verified that it receives a resizeEvent with the size decreasing a certain amount each time.