If you are using the line input on the Tracker, when you press play the audio coming in momentarily cuts out. This means that you have to have the Tracker’s sequencer running already in order to use the line input. That’s not very flexible.
I reported this on the GitHub issues page a while ago under ticket #1600.
I have the first type of the Tracker. I am uncertain if this problem happens on later models.
This happens on firmware version 16.0 and earlier versions.
This problem always happens. To reproduce the issue, create an empty project, unmute the line input in the mixer, play some audio in through the line input. Now press play on the tracker.