Keychrons have terrible build quality.
I'm not dissing your keyboard, I own 2x K2s and 2x K6s myself, so I know.
Open up the keyboard, and check the back of the PCB, there are alot of things that can cause this, everything from cracked traces, stray solder, broken terminals.
Be careful if it's a battery model, when you lift the pcb, do it gently so you do not damage the cable connector.
When you tighten or loosen the side screws, do it gently, or they will strip.
Take some high resolution pictures.