So I add a lot of bars of guitar chords, then Generate Chord Symbols From Selection. Boom. I get the chord symbols for the Acoustic Guitar.
And I get chord symbols for Electric Guitar, Bass and Piano, which, as my mother-in-law used to say, is too much sugar for a dime. 
How to turn that off?
Chord symbols are global. i.e. if you have chord symbols activated on Gtr, Bass and Pno, they will all display the same chord by default. I suspect this is where the issue is.
You can select the unnecessary chords and hide them if you don’t want them visible but if you try and delete one, it will get deleted in all staves.
Or, if you don’t want any chords in a particular stave: