Nothing jumps out as being wrong with that.

Is it 100% of the time only certain slaves work from certain windows? If you spam cast from one window do the others never do anything? Do you get error messages?

If you swap the spell name on just the ones that fail to work to, say, Wrath, do they work?

Try putting a /say or /emote in the macros so you can see if they're even registering as being clicked.