I know theres another of this topic, but my prob is slightly different. I was able to hit double or nothings and dismount quite well a while ago, but now, its like i can get into the mount, but when i drop my non-throwhand index finger, the thing drops all the way down, instead of a ‘left ½ mount’. Anyone know of this?
Yeah, that happens to me sometimes. Your problem is that when you drop the string is missing the gap of the yoyo. When you pull your finger out and drop the string make sure its aligned with the yoyo and the yoyo’s gap. That should help. 
Also, try to make sure your yoyo isnt tilting when you drop the string.
Have Fun Throwing,
~Samad