every cut, fresh edge, is a potential for it, seen it many times... what happens is the solvent in the freshly applied primer will eat into them and cringe the old stuff... especially if any of the substrates are lacquer... and I'd put good money on that gray layer being gray lacquer primer...
also if the edges aren't nice and gradual, they can show thru your primer.. requiring more primer blocking, etc to get flat for paint...