During recovery, it takes some time for the wrap to heal and settle into place. Because of that, it's actually possible for some acid to escape.
That said, I was told long ago that "the esophagus is a dumb organ" and that any pain is interpreted in the same way...thus the heartburn feelings can occur even when the pain has other causes.
In addition, while the wrap is healing, sometimes food gets held up at the wrap site, and starts to decompose/ferment, creating a painful situation. Even liquids can get held up there during the early weeks of healing.
As you know, a redo is even more complicated than the first surgery, so I would suspect that the healing is more challenging as well.
It will take months of healing, as you know, so try to be patient! Anyone who has had a Nissen has moments of panic when he/she feels reflux sensations. (I certainly did!) It's not fun to have those thoughts, but it's totally normal!
Hang in there!