Feedback on my FL/PE2

For some reason I am not able to roll on my lower back (it's abrupt).

The instruction page says "An arched lower back will prevent a smooth roll. " but I do not feel like my back is arched.

Also do you have any tips from preventing my legs from changing the angle to my body while rocking?

It does look a bit abrupt. Are you able to complete PE1 with your lower back against the floor?

In these reps you are lifting your head a bit too high and rolling too high up on your butt. Spread it out, lower it down. There's a reason hollow body position is also called 'dish' shape