the correct way to position the arrow is with the cock (feather) up

Fascinating stuff, Robert - thanks.

I still think that if an archer's shot went awry because of feathers (cocks) being misaligned it may have been called a cocked shot. And perhaps if the shot span upwards (would that be because of the uppermost cock getting caught?) the archer would say the shot had been cocked up. So if you treat "cock" as a (derogatory) verb rather than noun cock-up would be a shortened version of cocked up - and the latter is still in common usage here:
"This is really cocked up" = "This is a real cock-up"

Total conjecture, but to me this has a real ring of plausibility about it.

Which simply means that I like it

Fisk