Instrument following Chord track when it shouldn't be.

Follow Chord Track means something different than what you are thinking.

It does not mean that the Track plays whatever the Chord Track has on it (that is enabled elsewhere). When you have Follow Chord Track enabled then anything you play or record onto the Track, for example from a MIDI keyboard, the Notes you play will be forced to conform to the Chord Track. So any key you hit will always be in the Chord and/or Key depending on the specific settings.

To have a Track play block chords of whatever is on the Chord Track you need to set that on the Chord Track itself. You can set it to play on one single Track OR on all the Tracks that have the Monitor button Enabled.

If you would like more control over what Tracks play the Chord Track, here is a method that uses Virtual MIDI Cables to make the Chord Track appear in a Track’s Inspector like any other MIDI source.