Any idea how to lock the deck once a track has been loaded to stop accidentally adding another track during playback to the same deck. Im using the DDJ-RX.

its in Rekordbox once Performance mode is enabled. Go through the settings, its in there. I am not home to check so i can't tell you exactly right now

according to the owners manual it under settings/controller

Preferences: Controller
DECK

Eject/Load Lock
Select [LOCK], and music files cannot be loaded to the deck while a track is playing.

Many Thanks