Hello, himalaia
This is the procedure to reset Pitch Bender and Ribbon Controller, described in the OS update readme :
1) Turn on power while holding [OSC2 SYNC], [-12dB/-24dB] and [FILTER TYPE] to enter Test Mode. Wait until display
indicates "[1] MIDI Test."
2) Press the [3] button to display "[3] Bend Mod."
3) Push the bender lever left fully and gradually return it to the center. Press [LOWER].
4) Push the bender lever right fully and gradually return it to the center. Press [UPPER].
5) Push the bender lever to the MOD position and then gradually return it to the original position. Press [KEY MODE].
6) When the '*' appears on the display, press [UP].
7) From the previous display, press [4] to display "[4] Ribbon."
8) While pressing down on the left edge of the ribbon controller, press [LOWER].
9) While pressing down on the right edge of the ribbon controller, press [UPPER].
10) While pressing down on the center of the ribbon controller, press [KEY MODE].
11) When the '*' appears on the display, press [UP].
12) Turn off the power of the JP-8000.
Mgomes