Everyone should keep in mind one of the only CTDs that we know of that occurs in conjunction with battles occurs when you are fighting an enemy with reinforcements. Sometimes it CTDs upon leaving the battle. Sometimes it doesn't though.

My suggestion is that before you fight any enemy with reinforcements, you definitely save the game. And I wouldn't fight any big epic ones against enemies with reinforcements either *unless* I was going to be ok with autoresolving it the next time *if* it did CTD upon exiting to the battlemap.