KETRON is similar to Yamaha with the triggering which triggers in sync with the beat.

The problem on the Korg is it appears to 're-trigger' when you press the fill in and as such if you press it slightly off beat, it 're-triggers' the chords (especially the chord track with a percussive instrument like Piano or string instrument like Guitar which are more noticeable). If you mute these tracks, the fill in/break works well.