I have lost almost all of my ability to execute this shot.
This happens in all areas of the game--you'll have something that you're good at, and then seemingly all of a sudden you lose your ability to execute. A couple of thoughts:
1. You learn by repetition, but repetition makes you learn the thing you're repeating. If it's something that you haven't done in a long time, practicing a fair amount is a good idea. If you are practicing a lot and something vanishes, you need to either take a (long) break or change how you're practicing.
2. Take 2 steps back if you're struggling; if you normally crank dead-bar pulls and you start spraying them, drop down to 2-finger off of dead bar. Practice that for a while, then go to 1 finger. Practice that until it's rock solid. Only then go back to trying the dead.
On the snake, slow it down and/or shoot shorter to the side you're working on; gain confidence with that and then ratchet it up.