Like BC, rob and jay said, I am thinking rebound damping and sag as well.
You´re actually compressing the bike with your weight in a corner, then you lift it up and throw it to the other side, which will unload the suspension.
The rear is losing grip, because the shock doesn´t let the tyre/swingarm loose quick enough. In a good video I saw, Max @ Traxxion.com said the tyre is "looking for tarmac" or sth similar. He mentioned correct sag is important. Maybe your shock spring is way too soft and in addition to that, you have rebound set too slow?
Loosening rear preload by clicks? Usually damping is adjusted by clicks and preload is adjusted with a spanner using these little collars. The metal rings that sit on top of the spring:
Rebound is at the bottom, vice versa to the front forks.
996/748 Suspension Setup
Worth a look. But in the end, I am not a pro.