Keyboard is not fixed after replacement

I recently spilled half-cup of tea to my macbook. After drying it I turned it on and found out that left shift key was always in pressed position. I tried to unmount the keys and clean under them but it had no effect.

So I ordered a new keyboard and replaced it on my own (was doing it first time in my life). Everything seemed to be ok, after a short period of time left ctrl stopped working. Of course I was upset and thought that's my fault and I didn't do replacement work good enough. But after some time left shift become stuck again (not the button itself but it's software status).

And now I'm confused, how the same keys could be broken again on the completely new keyboard? I've changed the board itself all the keys with pressing mechanisms, wires going to motherboard. The only original part is backlit layer. How can that happen? Maybe I should try to plug and unplug the keyboard wires from the motherboard?