Reedo's script has an error in it when certain things happen like when a party member K.O.s another party member via "confusion" or when a spell is reflected from the enemy to one of your party members.
One solution is to not use those things which trigger the error in your game.
Here's his response to the issue in another topic (I don't really know ruby scripting so I can't personally help you implement the solution) :
I apologize but I was unable to get a working VX ACE environment going so I can't do much to test any edits to the script. It's also been a while since I've worked with any Ruby and probably won't use it much anymore. If I get any time to play with RPG Maker it will most likely be spent converting some of my other scripts to JavaScript for MV (this script is no longer useful in MV but some of the others are).
You should be able to get past this issue though with a simple code edit... just test for nil on line 585 and skip the following code if there is no reedo_guard value. I suspect you've just run into my override for default guard behavior and it is failing when there is no guard action available. Skipping the code which cares about the guard action should be safe to do (shouldn't have unintended consequences) and should resolve the error.
