Client/Server Lag, causing Grimoire (or rbot) to glitched out. Also cache.
if you're using grimoire, Join: room ones won't rejoin if you are already in that map unlike packet ones where you can but kind of sucks when making a stable bot. Also if you're using packet ones, when you minimize grimoire while the code block (?) of Join packet is about to be executed, you'll experience eternal loading.
if you're using rbot, doesn't matter. Both of them does the same function.
Edit: Join Packet (grimoire) is useful before when respawn timer sucks. I don't know what's the best use of rejoining packets in grimoire anymore.