only on 1 toon does this happen outa 9 when zoning my merc will still be in group but disappear zoning did help but as of last night that doesn't always work I know a lot of people have said its not because of the changing the mercs name but its only on the one I did change the name on 2 mercs that they disappear and even at one point I had both my mercs in the group window.
Post it here maybe? https://forums.station.sony.com/eq/index.php?threads/update-bugs-11-14-13.205134/