My front door has side block on each side, built with building bricks and a concrete slab on top. Last year, when those building bricks start deteriorating, I asked someone came to lay a layer of "man-made" stone-like concrete panels on top of those bricks. Installer first nail a metal wire mesh on the original bricks surface, then use cement to glue these stone-like panels on top. Less than 18 months, all these stone-like panels separating from the bricks (see photos). But they still glue very tight that I cannot pull to move them by hand. So basically they are not falling off, just separation.
What is the best way to repair these separations? and What is the easiest way to repair these separation?