Another workaround that may help find the reason of the bug : in the non-resizable window, click on Settings, that will open "Software and Updates" window. After closing this window, the software updater window will be resizable.
Another workaround that may help find the reason of the bug :
in the non-resizable window, click on Settings, that will open "Software and Updates" window.
After closing this window, the software updater window will be resizable.