Kluluen

Sorry to hear none of the fixes worked. Have you identified the exact LED with the issue (red green or blue)? Not exactly a fix but I set the whole keyboard to each color (red, green, blue) and only on the green did my key look dimmer. Did you have any luck with corsair support? Ha ha ha I try keep a copy of old firmware/cue installs.....in case of firmware-apocalypse.

Funny you should mention banging it against the wall.... This happened to me once and I ended up wailing on the key for a bit and it cleared up. For me it was the V key. I think a piece of debris got under the backplate through the hole under the space bar and was covering part of the LED. Shaking the keyboard might have been more effective but cant really say since I haven't run into the issue again.