The solution seems to be to kick out the offending member (the one who has, in the above-mentioned example reserved the sandwitches) so changes to library parts can be sent by the user that edits them and subsequently, everyone else can send their changes as the issue of "somebody is sending changes to library" is solved.
Anyway, what I am truly interested in is why this happens in the first place, especially why the button to send changes only from the library manager (or individual library parts via contec menu in lib manager) seems to not work?
From Archicad 8.5 all the way to the present.
Passionate Autocad hater as well.
Wish to save palets and menus individualy in work enviroments: