Weird thing is it's just this specific combination.
holding L and J, and for some reason A (and only A) doesn't register
holding L and J, and for some reason A (and only A) doesn't register
Comments
And on your keyboard, you've tested to see the actual number of keys you can have depressed at once? (I used this tester: https://www.mechanical-keyboard.org/key-rollover-test/)
(this keyboard is also getting old too, 10 years or so, so maybe its just showing its age)