I have seen this on the board elsewhere - my Z20 keyboard has about a half dozen keys that feel sticky and don't respond normally when pressing them.  Right out of the box the 8 key was completed pressed down.  I sadly had to revert to my old keyboard.
 

Maybe something happened but you could try and remove all the keycaps with a keycap puller and wash the plate with some rubbing alcohol and q-tips while rinsing the keycaps in some soapy water