I put a boraxed skin on a bow last week. I rinsed the skin for a long time but it still had a few places it didn't stick, very small places but noticeable when I held it in the light.
On the places between the edges I slit the skin along the edge of the pattern with a very sharp knife, small split, about 1/8th" long. I inserted a sharpened toothpick at the end the split to hold it open and put a drop of super glue under the skin. I pressed the skin back down, wiped away the excess glue quickly and had an invisible repair. The unattached place looked like an air bubble under the skin.
I use super glue on lifted places on the edge as well, same procedure. Lift the skin up with a sharp knife and put a drop of super glue under the skin. Press the skin back in place and you have a permanent repair.