Hello, Ive noticed this while doing boss runs.

 

Destiny bond doesnt appear to work as intended if the target is full health and holding a focus sash.

 

When I battled Oak, and Wobbuffet used destiny bond on his Charizard, it didnt take it down the very next turn when the Wobb died. instead it appeard to break the sash, since the next wobb was able to one hit it with mirror coat.

 

Hope it makes sense, if not let me know :)

I want to add, I think this is also applicable to mons with sturdy. I remember seeing something weird happening but wasnt so sure what it was before.