There are some things to keep in mind here.
Contrary to what seems to be popular belief, the grab release is not essential to get the "infinite" off. It's just a quick setup to get the right distance Luma needs to start it. It can started any time the Luma gets you in a jab.
The Training mode combo meter still suffers from inaccuracies, but one thing to note is it only checks to see if hitstun is expired before the combo meter is broken. There are strings where you can "combo" outside of hitstun where the hitstun has ended, but the opponent lacks the frames to defend themselves from a followup attack since defensive options do have a small startup time. This is one of those followups.
There are no frame 1 escapes Sheik has to protect herself from attacks aside from shield, and since you're 1. in the air and 2. even if you land, there's a brief period of 3-4 frames before you can act anyway, Sheik cannot actually escape it despite what the Combo meter would have you think.
As for whether DI/VI works to break it, I don't know because I haven't had a friend to test this with yet. The AI definitely does not know how to break it. But if it is escapable, it's not by virtue of the evidence @
Tristan_win
provided.