You have a Linux distribution with Xorg and you have configured the keyboard layout switcher to use alt+shift to switch between languages. But once you do that, keyboard shortcuts that use alt+shift+<key> combinations cannot be used. The same could happen if you have selected ctrl+shift as a shortcut to change language which disables all ctrl+shift+<key> combinations.
Libreoffice is free, no question these guys should be congratulated for their work and of course there is no intention to bm them.
However some things are noted as GUI fails.
Like this one: If you want to insert a new line directly under a table, you have to press alt+enter (and hope it will work).