When I "hammered" the frets on the flat fretboard, it was quite straightforward, all of them were seated properly for days until ... I glued it on the neck and after the finishing work. I start stringing and notice many of them pops up slightly in the center.
So I used a small block of steel (which I also use as my fret leveling check tool), and a clamp (as a vise) to press each of them flat down again. This works great for all the frets #1 to #10 and they stay put. Fret#11, and #12 are where the curve of the neck heel is. Clamping is not possible as the clamp will slip due to the curve.
For the higher frets that are right above the heel and the head block, I can press them down as described above, but not the ones beyond the head block. There is no support for pressing, I do, it will break the back board.
I did use cauls to during this work to ensure no dents is created due to the "pressing" action.
If I am not mistaken, "hammering" the frets down during the setup phase is not a good thing to do.
I need a recommendation as to how to press these down (fret#11 and #12).
The pop up just a little bit at the center enough to cause buzzing at center strings, outer strings are OK.
I can file them down but this would be my last resort.