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

To be aMASTER, the loaded track must fulfill the following requirements:
-It must be analyzed in the rekordbox.
-It should be loaded in Library Browse.
　(If the track is loaded in Folder Browse, it does not become the MASTER)
-The track must have a BPM of 40 or more at a TEMPO of 0.0%.

The following are the conditions to auto-switch the MASTER. It operates on the following specifications when the track fulfilling the requirements to be MASTER is on the left and the right DECK:
-The DECK that has started the playback first becomes the MASTER DECK.
-If the MASTER DECK is paused (PLAY and CUE buttons are pressed during the PLAY and JOG is touched) or has a track loaded, MASTER moves to the DECK with PLAY status. (Does not operate when paused.)