Reloading should be used for testing, not in the middle of server running.
Otherwise there will be problems when for example when all tables will be erased and they wont exist as mentioned above and scripts are reset, so if you have some event on spawn for example, the script wont run properly as the creature already was spawned.
Creaatures in combat with scripts and phases and spellcasting in on enter combat will not have triggered since the events will be reset.
This means if someone was battling a boss and you reload, the boss no longer casts spells etc.

So be wary of what you are doing :)