Cherry MX 3000 no longer consistently registering keypresses

[Logological]

Dear all,

I have a Cherry MX 3000 USB keyboard that I bought back in 2014. As of last week it's no longer consistently registering keypresses—about 20% of the time, when I press a key nothing happens.  Needless to say, this makes it supremely unsuitable for any sort of typing—even just logging into my computer takes four times longer than it ought to.  The problem isn't limited to individual keys, but rather seems to affect a large number of them, or maybe all of them.  For a while, unplugging the keyboard and plugging it back in again seemed to solve the problem, but the problem would return after a few minutes.  Now unplugging and replugging seems to have no effect.  The keyboard isn't particularly dirty on the outside, and nothing has been spilled on it.  I've tried blowing on the keys and also turning the keyboard upside down to gently shake out any crumbs or debris, but this hasn't helped either.

I don't think the problem lies with my computer, since I've got another keyboard (the same model) which works fine with it. Likewise, the defective keyboard exhibits the same defects when plugged into a different computer.

Any idea what the problem might be, and if there's an easy way of solving it?  I'd prefer repairing rather than replacing the keyboard if it's an option.  If all it needs is a cleaning inside, maybe someone could point me to a video showing how to open the case correctly.  (I think it snaps open somehow; I don't see any screws.)

[Findecanor]

My guess is that there is a problem with the connection of the USB cable inside the keyboard.
I would open up and see if there are any breaks or bad solder joints. Sometimes a poorly made solder joint could get loose years after it had been made.
Do also take a look at the solder joints to the cable between the controller board (which has the LEDs and IC) and the switches.

To open up the (modern) 3000 case, get a wide flat screwdriver and pry the snaps on the bottom. There are different snaps at the front and the back.  On each side, start in one corner and work your way along the edge to the other corner to avoid them snapping back.

[Logological]

Thank you.  With your hint I was able to pop open the case.  There was quite a lot of dust inside, which I blew out.  I checked for loose solder joints and cables but didn't see anything obvious.  I put the keyboard back together again and it seems to be working now, so hopefully the recovery isn't a temporary thing.