So as of now, I just defeated Bramble. All I did was stop attacking the boss if it tries to attack/use a skill then I attacked the boss while it is walking or the animation of the attack/skill is still on going not while the boss is casting/preparing to attack. This is based on my encounter though 
I found that it also helps to uncheck all your graphic settings and put performance in low mode. Hope that helps!
Also noticed every time I crash, all bosses that causes the crash use the same skill that shoots pellets/bullets around 