Newbie Pad Problems, Please Help

Hey there, friends, I have a 2500 running jjos 3.12, just bought it a week ago and love it but I have an ongoing problem with my pads. I say ongoing because this happened the second day I had it and then it went away. Now it came back and it's maddening. Whenever I hit a pad in the fourth column (4, 8, 12, 16) it triggers all the other pads in the column. I took it apart and tried to clean the pads, but it didn't have any blemishes and nothing looked particularly off (then again I don't know what to look for). I put it back on and it's kind of worse, whether it's on full level or not. Do I need new pads or is it worse than that and I need to replace actual hardware components? I have midi off, no daw, I'm simply using it as a drum machine in the same style as araabmuzik and jeremy ellis.
Thanks guys.

Well its like you said its probably a sensor problem.

You should do as you aldready did: open it up and try to clean em.
That should do the trick. (the sensor sheet under the pad that is)

If it doesnt work and/or some of the pads arent working = you need a new pad sensor sheet which arent that expensive + easy to install.

No worries mate, machines who are second hand are all sooner or later gonna need some love.

When I put my 2500 back together it didn't quite sit right and caused a similar issue. I believe it was from the panel not quite sitting perfect and then being a bit too tight in its new seating. Loosening the screws holding it together helped quite a bit.

Obviously you don't want the thing falling apart but if you over tighten it then the vibrations from tapping one pad are translated through the chassis to other pads. YMMV