It is server sided, it happens to me too on ragnarok, I even had freezes then a Bluescreen after being Teleported by a party member. the music stops, i can move but my animations are stuck on what i was doing before the sound stopped (running, for example). The menus on npcs for menders etc won't show up, I won't do any attacks, anything. after a while they work again for a few seconds, then it happens again.