Several of us have had problems similar. Roland no longer sell the parts, including the PCB they are mounted on. If you aren’t a very experienced user with good soldering iron skills, I think I’d recommend getting the replacement sliders and have a qualified tech (someone familiar with keyboards) do the job.

But yes, if it’s the slider for bass volume, it’s unlikely you’ll ever need a full 127 on the slider. And if you DO need it louder you can do some EQ tricks or use an MFX to add some boost, or change the velocity curve to LOW or fixed (fixed works pretty well sometimes with bass parts… remember, organs have no velocity sensitivity and still manage to provide a solid consistent bass level).

One of the pleasures with the BK9 is that there are so many different ways to address a problem..!