I don't understand the conditions by which the sync master switches.

First, as a condition to become the sync master, the loaded track must fulfill all of the requirements below.

-It must have been analyzed with rekordbox.(A deck cannot be set as the master for tracks that have not been analyzed.)

-The track must have a BPM of 40 or greater for a tempo of 0.0%.

-The deck on which playback was started first is set as the master.

-When the pause operation is performed on the master deck (by pressing the PLAY button during playback, pressing the CUE button or touching the jog dial), or when a track is loaded, the master deck switches to the currently playing deck. (It does not switch while in the pause mode.)