I am in a similar situation, with a similar system. I bought the disc release and have had constant frame chugging. I was lagged through the last decision in episode 1, the ending maybe half hour of the first episode being the worst offender so far although it did not stop in episode 2.
I am tempted to return the disc version and opt for the digital in the future unless there is news of a patch in the works.
As whiny as that sounds, it's only because this issue is interrupting a fantastic experience. Thanks.