What water test?
LIFE'S TOO FVKING SHORT FOR SAFETY!!!
BTW, I have applied lighter on the space bar because I thought that it was wonky/not straight. Didn't work.
Cut cut cut the keycap extra stabilizer. Didn't work.
Then I cut the four plastic corners around the stabilizers on the keyboard (don't worry, it was the Ducky Zero Shine (Stabilizers can be replaced right? Right? RIGHT?)). Didn't work.
Then I see see the actual (+) thing on the key insert... and realized that the ABS-like material is too flipping thick for the key to insert itself correctly into the switch and come out without brushing against the switch cover.

Bloody heck. Shave shave shave. Still sticky. Shave some more plastic. Finally worked.
Should have been playing Dota instead, but just watched some games while fixing it. Running up and down looking for my lighter and knife...
Replacing plate mounted Cherry style stabiliser is much more works and cost requiring... Good luck for dat...