Yips are like back pain ... if you've never experienced it - you might want to think twice before commenting.😬 And I've had both. The yips definitely DO exist. And there was no gradual onset. Putted well one year ... and the following year I could miss a 10 foot putt by 4 to 5 feet (yes, feet) to the left of the hole, or knock it that far past it too. For me it was the right hand, uncontrollably, flicking at the ball right at contact - especially on putts inside 20 feet. It seemed like the harder I tried to lock down the hands and arms - and make it entirely a shoulder rocking motion - the worse it became. It was like having an invisible gremlin living on the putter head - and you never knew exactly when he would pull it way left (other than often). Crept into the shorter touch chips as well.
Like FauxAmish, I switched styles - but, for me, it was to a "pencil grip". I'm still not as good of a putter as I used to be ... and am considering going to armlock to even further negate the right hand taking over.