Official comment
To all - our tech team has noted that this issue was already addressed with 4.2.0, but recommend you update to the latest version of rekordbox (4.2.5), newest firmware (2.2.0), and the newest drivers for Windows 10 (ver 1.210) or Windows 8.1 and 7 (1.200) - https://www.pioneerdj.com/en/support/software/xdj-rx/