Even if [CUSTOM1] is selected for [Customize] of TRACK SEPARATION function with DDJ-FLX10, PART ISO (VOCAL) cannot be controlled by operating EQ HI knob.

Update the DDJ-FLX10 firmware and rekordbox versions to the latest versions below.

DDJ-FLX10 firmware version 1.12 or later
rekordbox ver. 6.7.1 or later

Set PART ISO to EQ and MIDI assign to the default state if you've imported and used DDJ-FLX10 TrackSeparaton_Custom1.csv.
* The content customizing the assignment to the hardware on MIDI Learn will be deleted.

1. Connect DDJ-FLX10 to PC/Mac and activate rekordbox.
2. Click [MIDI] in the upper part of the screen to open [MIDI setting] window.
3. Click [DEFAULT] button and click [No] for the dialog "Do you want to save the file you are currently editing?".

MIDI assign PART ISO Inst to EQ HI and PART ISO vocal to EQ MID if you've customized and used MIDI assign.

1. Connect DDJ-FLX10 to PC/Mac and activate rekordbox.
2. Click [MIDI] in the upper part of the screen to open [MIDI setting] window.
3. Select PartISO Inst (Deck1) and PartISO Vocal (Deck1) on MIXER tab and click [DELETE] to delete it once.
4. Click [ADD] button to add [PartISO Inst] and [PartISO Vocal] to [TrackSeparaton].
5. When [LEARN] button is ON, select PartISO Inst (Deck1) and operate EQ MID of Channel 1 of DDJ-FLX10 to execute [LEARN].
6. When [LEARN] button is ON, select PartISO Vocal (Deck1) and operate EQ HI of Channel 1 of DDJ-FLX10 to execute [LEARN].
7. For Channels 2-4, repeat the steps 3-6.
   * For the settings of Channels 2-4, it is necessary to set 2-4 with the pulldown menu of Deck.