Sometimes the position of the playhead along the timeline can affect the sound of Software Instruments being played live. For example, in Jam Pack 4, many Software Instruments allow you to choose different articulations by mapping data from the modulation wheel on your MIDI controller.
The instrument remembers the last articulation setting it sees, whether it's from a recorded track or sent live as you play. However, when you move the playhead, the most recent recorded articulation for each track will be sent, which may be different than the one you're expecting. You can reset the articulation for the current active track by moving your controller's modulation wheel.