Respawn will only fix loose ammo (little things that fly and give you 3 more pieces). For powerups/morph boxes/crates you can shoot the general area for a little while and the powerup should come back in due time. JJ2 works largely over the UDP protocol. What this means is that you are not guaranteed to have powerups, trigger crate activation, player location, health loss, etc sent to you. While most of the time the packets do not get lost, it does happen frequently. Only downloading levels/tilesets and chatting are guaranteed to make it to every client. This works over TCP and is not implemented perfectly - servers crash when too many people talk and someone is downloading a tileset - TCP in JJ2 seems to get confused when too many different things are sent over it.