In trail riding my bikes back end seems to chatter (bounce) going into tight turns while chopping the bar. I think it is my rebound setting but not sure if it is high/low. From what I have read it seems that it might be set too low?
I've experience this problem when I use too much rear brake. Try feathering or staying off the rear and see if it clears up. I found that a change of rear pads helped quite a bit as my stock pads grabbed with very little pressure.