Just finished beating my head against the wall for something trivial, so I thought I'd post in case someone else comes up against it.
I have an action that uses the FILENAME to create the TITLE tag. It gets applied last, after case conversion and other actions.
As double quotes are illegal in file names, I use two single quotes to represent things like:
07 - More Than This (7'' Version)
but I want to use one double quote (") in the TITLE tag. I added a REPLACE action to deal with it, but I added it to my list of "standard" actions, which are applied to ALL fields and run before the last "Convert FILENAME to TITLE tag" action. That had the effect of undoing the REPLACE.
Separating the "Single Quotes to Double Quote" REPLACE to its own action and placing it after the "Convert FILENAME to TITLE tag" action caused my head to stop hurting