I was playing with my M-Kangashkan and he send a Smeargle that had King's Shield.
I used Drain Punch he switched into Smeargle. Then Smeargle used King's Shield and I used Fake Out because I already know that he would use KS and Fake Out hit the KS and I got lowered 2 attacks.
Why did Fake Out hit and didn't miss?
When vs. Aeglislash
When vs. Smeargle
It appears that smeargle's king shield and aegislash's king's shield follow different mechanics, or that smeargle, when using king's shield, causes a glitch where even when the opponent fails to execute a contact move it still has it's attack go down two stages. This is likely an oversight by programmers at Pokemon showdown, and it may be worth it to report this to the programmers at smogon.
Holp this helps and special thanks to my bro Aeternis