I've got it, and been fight'n the darn stuff for 25 years--the wrong way.
What is it? I don't know, but it's bad, very bad stuff. I started shooting left-handed. Funny, the stuff isn't on the left side, and since I know what it feels like, I've been able to stay ahead of it.
I "think" it's a breakdown, or short circuit of your form. It appears, in my case, to be a collapse.
If you can pull through your shot, you can't have the stuff. It's crazy.